Before the days of microtransactions and horse armor DLC, video game developers had to insert as much content into a cartridge as possible. Downloadable content was not yet an option and only a few games would release expansion packs. Developing a game for physical release has always been expensive and publishers wanted their money's worth, so developers had to utilize every bit of data. Game developers would add content such as characters or levels. Those employed to hype a game would only write about the main content of the game and it was rare that a game's secret content would make it into a press release. Players would have no idea there were hidden treasures inside the game.
Game cartridges were also expensive for video game fans decades ago. Instead of buying every new game at release, some players would just replay the games they owned. By taking their time and exploring every area, secrets and new levels were uncovered. Friends who traded games would also find new content and share those secrets with each other. Before the internet was common, gamers could only find out about these secrets from game guides on magazine shelves or from word of mouth. However, some secrets remained a mystery. After decades, game developers have revealed these secret levels.
Luckily for us, these hidden levels have now been uncovered by both fans and developers. This list is filled with spoilers. If you're interested in dusting off some old classics and heading on a new adventure, read on to discover how you can uncover some hidden levels.
15 Aztec Temple (GoldenEye 007)
GoldenEye 007 was originally released on the Nintendo 64. Within this game is the Aztec Complex, the 19th level of the game. The Drax Corporation has stolen a NASA shuttle and planned to use the Aztec Complex as a launch pad. Your task is to recover the shuttle and make it out alive. This secret level is not only hidden, but also considered the hardest level of the game. Guards carry multiple Moonraker Lasers and AR33 Assult Rifles. Jaws, the main enemy within the Aztec Complex, has a higher defense than most bosses in the game. It takes over fifteen precise headshots to take him down. Finish the level on "Secret Agent," or Normal difficulty and you will unlock one or two Moonraker Lasers to add to your arsenal.
14 Ziggurat Vertigo (Quake)
The Ziggurat Vertigo is hidden within the Quake's Dimension of the Doomed. You must find the key and escape through the exit. In this indoor level, you are trapped inside a temple and surrounded by hot lava. This level is true to its name, as not only are you trapped in a ziggurat, but you will also face vertigo-inducing effects. There are hazards surrounding you with the bonus of the gravity being 1/8th compared to other levels. You will also struggle to stay in control thanks to the gut-wrenching, disorienting special effects. Jumps over obstacles and missed falls are also longer and more challenging. Besides navigating the level, you will also face scrags, ogres, and shamblers. If you overcome the hardships, you'll be rewarded with the rocket launcher.
13 Out Of This Dimension (Star Fox)
Star Fox's hidden level "Out of This Dimension" also acts as an alternate ending for the game. Once you uncover this location outside Lylat system, Fox McCloud and his team will never leave. Within the vast space are colorful stars and moons with smiling faces. These background creatures are not aggressive and will keep you occupied until you reach the end of the level. These upbeat surroundings will disappear once you reach the Slot Machine end boss. To battle it, you must shoot the pull-arm. Different combinations on the slot machine will attack or heal you. Once you're tired of rolling slots, you can destroy the machine. You will then unlock a mini-game where you must spell "The End." After the mini-game is completed, the game will reset and can be replayed.
12 It Came From Red Alert! (Command & Conquer: Red Alert)
"It Came From Red Alert!" is a secret level that can be completed after finishing the main campaign. If players have the Counterstrike Expansion Pack, they will be able to access the secret content. After the defeat of the Soviet Union and Allied victory is achieved, players will have to head back to the main menu of the game. Holding down the Shift key and clicking the speaker will activate the campaign. You, the commander, will be tasked by Greek Officer Nikos Stavros to defeat the red ants. These enemies have escaped from a deserted research laboratory belonging to the Soviets within Europe. There are only four sub-missions within the secret level. In the last sub-mission, "Exterminate!," you must defeat the Queen Ant and rid Europe of the red ant plague.
11 The Son Of Dr. Tongue (Zombies Ate My Neighbors)
Zombies Ate My Neighbors features almost 50 difficult levels. In each level, you must rescue your neighbors from various horror movie monsters. The mayhem is due to Dr. Tongue, the main villain of the game. He has no problem creating chaos in the neighborhood, even if it means his son will become a victim. Within "Revenge of Dr. Tongue," players can stumble upon the bonus level "The Son of Dr. Tongue." This level can also be accessed by entering a cheat code. When you enter the level, you must rescue various neighbors, but also face various enemies and witness Big Baby clumsily walking in the yard. After your journey takes you to the laboratory, you will find his mutated son and assistant, Dr. Bug, a boy with the head of a fly.
10 Maian SOS (Perfect Dark)
Completing every level on Perfect Dark's Secret Agent difficulty will reward you with four Special Assignments. These missions give insight on how different side characters survived, escaped, died during the main story. In "Maian SOS," you take control of Elvis, a Maian alien. Elvis is fascinated by Earth and its inhabitants and can be seen wearing an American flag printed shirt.
In "Maian SOS," you awaken as a weakened Elvis. One hit will immediately grant you a game over. You must help Elvis send a distress signal to the Carrington Institute, who are alligned with the Maian aliens. Enemies will find it easy to spot Elvis' giant alien head, but, luckily, you will be able to fight back with various weapons around the level. On your way, you can sabotage the enemies' medical equipment. To gain a Perfect level, you will have to destroy any evidence of alien technology.
9 Triumph Of The Empire (Star Wars Rogue Squadron II: Rogue Leader)
Star Wars Rogue Squadron II: Rogue Leader takes players on an adventure to battle the Death Star. Though you will be able to control the heroes in the Star Wars series for the main campaign, the secret mission "Triumph of the Empire" lets you control Darth Vader. The mission takes place during the "Battle of Yavin," which originally led to the destruction of the first Death Star. It can be accessed by using a secret code.
As Darth Vader, you will control the TIE Advanced XI, on a mission to defeat the Rebels. Darth Vader must kill Biggs Darklighter, Wedge, and Luke Skywalker. Instead of the Rebels scoring their first major victory, Darth Vader stops them in their tracks. "Triumph of the Empire" is non-canon to the Star Wars universe, but it gives you the opportunity to play as the other side.
8 Secret Cow Level (Diablo 2)
After defeating Diablo in Diablo II, you can access a secret cow level. Start a new game, at the same difficulty level you just finished the game. Access a portal via the Waypoint system to Act I's Rogue Encampment. In the Horadric Cube, place the Tome of Town Portal and Wirt's PegLeg. Transmute and a portal will open which leads to the secret cow level. Within this level are large groups of cows. Unfortunately, they are also Champion Hell Bovines and regular Hell Bovine enemies equipped with Polearms. At the most difficult level, The Cow King boasts over 11,000 hit points. They're aggressive and ready to destroy you. However, the bovines and the Bow King drop unique items and sets, so it is worth the trouble to power-up your arsenal. The level can repeatedly be accessed, as long as the Cow King lives.
7 Inverted Castle (Castlevania: Symphony Of The Night)
In Castlevania: Symphony of the Night, if Alucard frees Richter Belmont from Shaft's evil spell, a secret quest will begin where Alucard must obtain hidden items within the castle. To get there, move past the Throne Room where Dracula was originally located at the beginning of the game, press up on the directional pad, and you will be transported to the Inverted Castle. This hidden level is a vertically flipped version of the normal castle map. The castle has a unique map and can expand the total map beyond 100%. The color schemes are also completely different, along with a variety of different monsters and bosses to defeat. Though the Inverted Castle is optional, it will unlock different endings. Alucard can collect Dracula's relic body parts to obtain one of the good endings.
6 Hangar 96 (Marathon Infinity)
Before Bungie developed the epic Halo series, they created the Marathon Trilogy. Marathon also takes place within space in the distant future and heavily relies on accessing computer terminals. Within the terminals was complex lore that players had to figure out. Though most games require you to hunt for the secret level, Marathon Infinity places clues throughout the game. The game features three dream levels where the player learns that the Hangar is home to countless armless and legless corpses. Among these corpses are terminals that contain important information when making decisions later in the game. These terminals all contained codes that reference Hangar 96. Combined with the hex codes from the terminals on the first and last levels, they are compressed and can transport the player to a new multiplayer map.
5 Sacred Ground (Cave Story)
Depending on the Japanese translation you play Cave Story, Hell is known as Sacred Ground or the Blood Stained Sanctuary. Though Sacred Ground is hidden, it is required to access Cave Story's "Best" ending. After obtaining the Booster V2.0 and Iron Bond items and defeating the Undead Core, the player can enter the Prefab Building and go through the open passage. The Sacred Ground offers three difficult sections. After making your way through, you will find yourself in the Corridor. This area is the only place where Misery, the Doctor's servant, can be triggered to be freed during the ending. From there, the final room, the Seal Chamber, can be accessed. Players will have to fight through four phases of the end boss, Ballos. Killing Ballos will free Misery and save the Island.
4 Wolfenstein (DOOM 2)
DOOM 2's secret level takes players to another game-- Wolfenstein 3D, as id Software developed both DOOM and the Wolfenstein game series. The first secret map of DOOM II, Map 31: Wolfenstein, can be accessed through Map 15: The Industrial Zone. Map 31 is a complete remake of Wolfenstein 3D's first level. The enemies and wall designs are detailed recreations of the id Software title. The Wolfenstein SS enemies are level-exclusive, but the attack dogs from the original game have been replaced with Demons. Players familiar with id Software's Wolfenstein 3D title will find most of the map familiar. Within Wolfenstein are additional secret items, including a BFG9000, megasphere, super shotgun, backpacks, and medical items. After navigating through the map, you can either head to Map 16: the Suburbs or another secret level, Map 32: Grosse.
3 Totally Forked (Earthworm Jim 2)
Within Earthworm Jim 2's eighth level entitled "Level Ate," you can access the optional ninth level "Totally Forked." To access this level, you must travel within Secret Room Number 31. The level is marked by a purple marker. Take too long to find this secret level and a salt shaker will dissolve Jim permanently. Luckily, the salt shaker will not follow Jim into the secret level. "Totally Forked" takes Jim onto ham and bacon mounds. While navigating through the level, you will notice various caged cows in the background. Large forks protrude from every area of the level and Jim must avoid these sharp obstacles. Within the secret level are items to aid Jim's quest, such as homing missiles and an extra life. At the end of the level is a light-bulb portal, which will transport Jim back to Level Ate.
2 Level 0 (ToeJam & Earl)
ToeJam & Earl's secret level starts at the beginning of the game instead of the end. Players can reach secret Level Zero from Level One, but additional items must be collected. Access to Level Zero requires you to find either Icarus Wings, Rocket Skates, or an Inner Tube. After you find one of these three items, return to the first level. In the bottom left-hand corner of the map, fall through a hole in the island and you'll find yourself in Level Zero. Here, you will find a lemonade stand and gain one extra life. Getting in the hot tub will refill your health. When you're ready to head back to the main quest, simply jump off the island. You will be transported back to the highest level you traveled to before continuing your adventure.
1 Over 200 Various Secret Levels (Super Mario Bros)
The original Super Mario Bros game has one famous Negative World secret level. It is a looping underwater named "World -1." Super Mario Bros does not have only one secret level though, as it contains 256 secret levels. Most can be accessed through jumping through false walls. If you own a top-loading Nintendo system and the Tennis game, you can also access secret levels. The level will change each time you perform a particular trick wit the cartridges and only the Tennis game and original Super Marios Bros will pull this off. The hidden levels are optional and not required to complete the game. They are all randomly generated and similar to the other worlds of the main storyline. If you're not quite ready to save Princess Peach, playing through the 256 secret levels will be a great warm up for the final battle against Bowser.