The most south-eastern point of the map in Mor Dhona (from the Saint Enioch research camp) is a long tunnel that leads to a strange, obviously artificial, door in fluro green, yellow and pink that is set at a strange angle (and encased in crystal).

The door isn't open yet, but when you get close to it, the game confirms the location as 'The Crystal Tower'. You can also see where this on the map by a large dark tower like graphic next to this location, although it's not yet identified as such on the map. That's as close as you can get to it at the moment.