Monstro City

From Herocopia

The underwater home of a race of intelligent monsters. While most or all of its inhabitants cannot breathe water, the city is surrounded by the Atmo-Sphere, a bubble-shaped forcefield which holds back the waters. The residents of Monstro City vary widely in form, color, and size, looking not so much like one species as many.

Madame Majestrix is the current queen and ruler of the city. Her son Rex Zorus is the prince.

When last seen, in the mid-90's, the city was in a demolished and abandoned state, almost all of its inhabitants vanished. This was the result of a war with the underwater beings known as the Trenchers.