Regula

A Class D planetoid in a remote part of the Mutara Sector, Regula has been described as "...essentially a great rock in space". That is, at least from the surface it does. In 2265, the planet was chosen as a test site for the Genesis technology. The Starfleet Corps of Engineers spent ten months carving a system of caverns out underneath the surface. A Federation research station called Regula I was placed in orbit to support the testing. ("STII: The Wrath of Khan")

After the failure of the Genesis project in 2285, civilian scientists continued to utilize the station. The caverns were closed for sometime afterward. The station was abandoned during the Second Federation-Klingon War, but in 2384, it was overhauled and re-occupied.