Here's a location that I'm using in my current Madlands Campaign. This particular site was inspired by the City of Human Skulls described in Edgar Rice Burrough's Out of Time's Abyss. Of course, I had to jazz it up and introduce several campaign elements, basically making the locale my own as I integrated it into the campaign.
My campaign world includes Hawkfolk in the mountain ranges, taking the place of such avian species as the aarakocra or the raptorans. However, the name aarakocra is just too cool and too classically D&D not to find its way into my game. That's why this clan of warped Hawkfolk are called the Kokora, and their aerie-city thus becomes the Aerie Kokora. It was fun to watch the faces of the players that got it when I first gave them the lore as part of an earlier adventure.
My players have gathered a majority of the information below, so I don't feel bad about posting this for your thoughts and insights. As always, your thoughts, comments and constructive feedback are always appreciated.
Location Name: The City of Skulls, The Aerie of Clan Kokora
Ambiance: The Aerie of Clan Kokora resembles adobe pueblos with humanoid skulls in the walls, along ledges and eaves, etc. Built for an avian race, most upper rooms have opening in the ceiling to the outside. On roofs, one can see columns topped with human skulls, painted white and blue/red/yellow (mostly blue).
History: Once a city of Hawkfolk, its citizens converted to the worship of Kalima, Mistress of Murder. The Hawkfolk of Clan Kokora are now corrupted and twisted by demonic influences. Assassination and murder are now the defining characteristics that determine social position and advancement.
Encounters: Encounters in this area are generally with Kokora or dinosaurs (in underground caverns and surrounding jungle regions).
Treasures: The Holy Anvil of Dworkin is kept within Kalima's Tower. Chests of treasures taken off of victims captured via fly-by attacks at night are also abundant throughout the city.
Hooks and Hotspots: The River of the Dead flows beneath the city, where remains are dumped for removal. Several caves and caverns along the path of the underground river serve as lairs for creatures such as otyughs and vermin. Kalima's Tower (a Temple to Kalima) serves as the palace for 'He Who Speaks For Kalima', the Priest-King of Clan Kokora. The Kokora do take slaves, which they frequently sacrifice to Kalima at the new moon.
Life Level: Medium (High outside the city, but Low inside the city)
Hazard Level: High
Difficult Terrain Density: High (built for flying people)
Resource Level: Low
Herbivores: Stegosaurus, triceratops
Scavengers: Pterodactyls, osquip, scavenger worms, velociraptors
Hazards: See humanoids
Humanoids: Kokora, humanoid slaves/sacrifices
2d6 Encounter 2 Otyugh 3 Humanoid Slaves/sacrifices 4 Kokoran Priest/ess 5 Scavenger Worms 6 Osquip 7 Kokoran Clan Patrol 8 Velociraptors 9 Pterodactyls 10 Triceratops 11 Stegosaurus 12 Tyrannosaur