The claim: US Marine Corps Base - Presently home to 30,000 Mariel Cubans and 40,000 Albanians. Total capacity unknown.
What it really is: Actually it's a navy base, not a Marine base.
Most of the Mariel Cubans that left Cuba actually ended up in the United States, not Guantanamo Bay, and while Cuban refugees do occasionally slip into Guantanamo Bay, the amount of refugees living there is no where near the 30,000 being claimed. In fact the most ever held there was 10,000 refugees.
There were Kosovar Albanian refugees there in the late 1990's, but only up to 10,000 were there at the most, and it was temporary until they were later resettled in the United States, or went back home to Kosovo.