Caverna autem Tempus

Description
The Caverna autem Tempus (or The Cave of Time) is the location of the Time-Gate that sends Kevin and The Librarian to the past (and eventually an earlier future of the past.)

History
The Caves are believed to be ancient, dating back to at least 3979 BC. The walls are covered in petroglyphs from across time. (maybe kevin and the librarian were the ones who built it?)

Time Gate Destinations
Each cave triangulates to Los Santos in the year 2020.

(It is unknown whether the year 2020 AD is the fixed date that the Time-Gate leads to as it also has led the two to 2077 AD.)

From 2077 - 2020 and vice versa.

From 2277 - 2020 one way.

The third cave's location is yet unknown but most likely also leads to 2020. It can be presumed that the year in which you enter the gate does not matter, you will always end up in 2020 (or 2077 if you are already there.).