Curse of the Crimson Throne
Most cities have sewers. Some can even claim dungeons and deep caverns beneath them. No city, though, has a complex system of subterranean tunnels quite like the Vaults of Korvosa. Modern Korvosa stands atop the remains of at least two other civilizations and integrates both of them in its design. As a result, the origins of the Vaults of Korvosa can be divided into several categories.
The Shoanti who lived in Korvosa prior to its Chelaxian colonization dug squared ditches into the earth to bury their kings, warriors, and other elites. Over these trenches they placed stone slabs found near the shale cliffs along the bayfront. They then covered these slabs with low mounds of earth, leaving only the narrowest of openings to allow for the later internment of additional people of importance. Dozens of these mound trenches cover Garrison Hill and scores more cover Citadel Hill and the lowlands surrounding Korvosa. When the Chelish colonists began exploring the area on which they founded their city, they quickly discovered the hollow nature of these burial mounds. As the settlers expanded their city, they slowly connected many of these trenches, paying their dwarven allies to dig tunnels between them all. Without any regard to the dead Shoanti buried there, the Korvosans then made these tunnels into sewers. Today, the sewers under much of mainland Korvosa make little sense, making random turns and possessing numerous festering dead ends, thanks to the haphazard layout of the Shoanti burial mounds.
Most of the Vaults of Korvosa are formed from natural geological forces of erosion or volcanic activity. These irregular caverns and caves delve deep beneath the surface of the earth, sometimes well beneath the water table. Other tunnels seem to connect to larger subterranean complexes, from which horrible creatures occasionally emerge. Thanks to the proximity to Conqueror’s Bay, many of the natural tunnels under Korvosa are sea caves, some of which occasionally collapse in on themselves to form sinkholes. Along the Merciless Cliffs and the western cliffs of Garrison Hill, these sea caves sometime bring down whole sections of the hill, forming deep but narrow cysts in the side of the stone. The most famous of these cysts drops beneath Palace Arkona.
A few worked tunnels of unknown craftsmanship have been discovered at the extreme south end of Korvosa. Of these, two simply go on for several hundred feet before they suddenly end at collapsed roofs or ancient sinkholes. One opens into a small collection of chambers under the modern Pantheon of Many.