Caspias?

Via Bayou Renaissance Man, a link to Speigel Online's article about Forbidden City of Oil Platforms: The Rise and Fall of Stalin's Atlantis:

In the 1950s, Soviet engineers built a massive city in the Caspian Sea off the coast of Azerbaijan. It was a network of oil platforms linked by hundreds of kilometers of roads and housing 5,000 workers, with a cinema, a park and apartment blocks... 

The foundation of the main settlement consists of seven sunken ships including "Zoroaster," the world's first oil tanker, built in Sweden. In Neft Dashlari's heyday, some 2,000 drilling platforms were spread in a 30-kilometer circle, joined by a network of bridge viaducts spanning 300 kilometers. Trucks thundered across the bridges and eight-story apartment blocks were built for the 5,000 workers who sometimes spent weeks on Neft Dashlari. The voyage back to the mainland could take anything between six and twelve hours, depending on the type of ship. The island had its own beverage factory, soccer pitch, library, bakery, laundry, 300-seat cinema, bathhouse, vegetable garden and even a tree-lined park for which the soil was brought from the mainland. 

Fascinating.  Google turns up some nice images of Neft Dashlari.