Dungeons. I mean, it's right there in the name of Dungeons & Dragons. You're more-than-likely going to end up in a few during your adventuring career. And if you're looking for some more to go through, the appropriately-named Dungeon Dudes are here for you with their Dungeons of Drakkenheim adventure up on Kickstarter. It's got more than 20 ruins for you to travel through.
From the campaign:
DUNGEONS OF DRAKKENHEIM is a Fifth Edition campaign for characters level 1 to 13 designed by the DUNGEON DUDES, Monty Martin & Kelly McLaughlin, based on the original livestream game broadcast on YouTube and Twitch! Fifteen years ago, Drakkenheim was destroyed by an eldritch storm of falling stars. Now, the city is a dismal urban wasteland contaminated by otherworldly magic and haunted by hideous monsters. Fantastic wealth, lost knowledge, and powerful artefacts lie ready for the taking by adventurers brave or foolish enough to venture into the ruins!
Explore over 20 ruined urban locations including haunted streets, decrepit sewers, shattered mage towers, baroque cathedrals, and ancient castles inhabited by dozens of nightmarish new monsters inspired by dark fantasy and cosmic horror. Each site features evocative descriptions, gorgeous illustrations, and detailed maps. Personal quests, tantalizing rumors, and lightweight urban exploration mechanics allow player characters to experience the ruins in a nonlinear and open-ended fashion.
These strange crystals are found throughout Drakkenheim. The vast arcane magic within Delerium may fuel mighty new spells and magic items, but the stones emanate unnatural energies which induce madness and monstrous transformations. Unspeakable abominations have emerged from its contaminating influence, and bizarre Arcane Anomalies are triggered by its chaotic whims! During their adventures, characters can research ways to harness the power of Delerium, study its otherworldly origins, and discover means to protect against its deadly contamination!
The campaign's over 20x funded with 31 days left to go.