Diego Garcia
This is one of the most secretive military bases that may, or may not exist. Built on an atoll, which is a hollow island with a lagoon in the centre, this base is located in the Indian Ocean. In 1966, the UK confiscated the atoll from the natives, deported them to other islands and built a joint UK/US base.
Now, it’s all shrouded in secrecy. It’s been a launching point for incursions into the middle east, a CIA Black Site for renditions and has one of the largest Air Force fleets in the southern hemisphere.
And, despite international justice courts and the UN ordering both the UK and the US to shut down the base and return the island to the natives, both have raised their collective middle fingers and gone on with their secrets.