Looking for a truly epic location for your players to end up in? How about a palace with 1001 rooms? That's what you get in the very-appropriately named The Palace of 1001 Rooms supplements. Chapter 7: Crypts of the Underworld, which brings you rooms 601-700, is up on Kickstarter now.
From the campaign:
Get ready for the next chapter of the greatest mega-dungeon saga in RPG history! Enter into the Crypts of the underworld! In this chapter we will explore the saga of the hero's journey into the underworld through the lense of Egyptian mythology, as we unearth lost fragments of old D&D lore as well as the overlooked tidbits of historical legend.
What is the Palace?
The Palace of 1001 rooms is a fully illustrated, 5e compatible, OSR-flavored mega dungeon RPG module of unprecedented scale. We are currently producing it as 10 chapters of 100 rooms each in a PDF format with optional bonus art like monster tokens & VTT maps.
Each time a character steps through a portal in the palace, it connects to another, randomly determined room in that chapter (or the entire palace, at the GM's discretion). A d100 (or d1000) roll is used to determine the room a portal connects to. Each room is one page, and the room and page number are one in the same.
The campaign's up and running now with 28 days left to go.