Could it be:
1. A huge flying saucer (UFO_USO) that floats above a black hole.
2. A solid construction that can open and close leading to an underwater base.
https://earth.google.com/web/@-14.22603786,-81.70339375,20.17905308a,47968.73641003d,35y,25.00972204h,0t,0r