Not sure where to go. Spoilers

[Amrath]

I've just done the section in Reflective Sky where you get the mine key, so you can get into the tower.

Despite passing the building earlier, where do I need to go next?

[Sage Of The Wise]

You have to go back to the lost city area(The screen before Altair Mansion) and you can enter the houses in the north part of the area, which has a elevator in it that brings you down to the minds.

It might also be a good idea to do some of the sidequests now if you havent done them yet.