Lake Raydia is the largest, and only, lake in Chroma City. It sits at the top of the city surrounded by six districts and blocked at the south - eastern edge by the Chroma Dam.
The lake is most likely a reservoir, given Chroma Dam acts as an barrier. The exact specifications of the lake are unknown, but it is safe to assume that the lake is large enough to render seeing any of the six locations at any point impossible. The lake is also deep enough at the center for the INKT ship to remain there during the occupation. Most of the coastline along the lake are all artificial constructs. There is only one island within the lake: Guggentraz Island Prison, located to the east.
Furthermore, there are no suggestions to know if there any natural inputs into the lake (i.e. rivers). Any volume of water that flows into the lake comes from large pipes, carrying water from an unknown source to the lake via canals and water pumps. Another mystery is how do the container ships from both Docklands and Raydian Docks leave the lake.