Beneath the streets of Nectar lies an extensive labyrinth of tunnels and passages. The ancient sewer network runs everywhere, draining wastes into huge underground chambers where it ferments to generate methane gas. Cellars and underground passages remain from buildings long since demolished. Hidden treasure vaults and secret chambers are everywhere. Over time, much of Nectar's underground has been connected to form a vast secret city.
The marshy soil of Nectar means that much of the underground is flooded some or all of the time. In some of the sewer tunnels, lethal bacteria thrive in the filth. Dangerous creatures thrive in the darkness of the Deeps _ blind cave snakes, hunting by body heat; swarms of venomous scavenger lizards; and the tentacled horrors known as Knoe Shonsu.
Many people live in the Deeps and none of them are the sort anyone would wish to meet. Smugglers use the underground chambers to hide contraband and move it past the eyes of the customs inspectors. Bandits sometimes take refuge below ground. More than a few unfortunates in the final stages of madness induced by the rotting disease, Che'peech, roam the tunnels.
Rumors tell that Nectar's Deeps extend far below what is known. Drunkards in the Entertainment Sector tell wild stories of huge caverns far below the city, where creatures from past ages of Mars's history still lurk. Others claim to know of functioning Canal Builder complexes hidden beneath the Old City.