I went down to the bases through the Galaxy Disco, went to both bases, killed mostly everyone, used the two terminals to start the explosions, and now im back in the abandoned station the bridges the two bases, and I have no idea where to go :(

Help!

Go through the hole in the wall next to one of the computer terminals you used to trigger the explosion. Now look for a hole in the floor and go into it. You'll be in the tunnel leading to the entrance to the Lost City.