Imagine a Skyrim that was hit with a terrible ecological disaster--like a meteor strike or a terrible famine or a flash flood or something. Imagine it was so bad that everyone picked up and left, leaving just abandoned, broken-down towns and buildings behind. Now imagine that, but it’s real because someone made it.
Modder Scrabbulor’s "Alternate Skyrim" mod is "a broken mostly empty Skyrim with opened cities," where "only undead, creatures, and animals remain." Every city, town, and settlement has been vacated to the point where you’ll rarely see another soul. Ralof will make an appearance in that cave at the start of the game, and you’ll sometimes see sailors willing to take you to Solstheim, but other than that, this is the Abandoned version of Skyrim.
Walk through Riverwood and you’ll find the blacksmith’s house gone, with fallen-down planks the only sign of its former existence. The Sleeping Giant Inn and the Riverwood Trader general store are gone, their rooves collapsed, and their doors broken. There are no dogs, no cats, no chickens, and least of all, no people. Just blowing wind and the sounds of nature far off in the distance.
Whiterun is even worse. Most of the buildings are still standing, although Severio Pelagia's roof has collapsed, and every door and window that remains has been boarded up. Windhelm is in ruins with parts inaccessible due to rubble or collapsed walls.
Scrabbulor explains in the mod description that Alternate Skyrim was originally part of a larger alternate timeline mod, but they decided to release it on its own for other mod-makers to use. "The potential for Medieval/Hyboria/Singleplayer/Co-Op/Survival addons felt worth the effort," wrote Scrabbulor.
You can play the mod yourself, but with everyone gone, there's nothing for you to do but wander a very lonely Skyrim. Maybe somebody will use this to make a zombie apocalypse mod for Skyrim one day. Or maybe they'll fill it full of Chinese spy balloons.