the capital building is pink Granite.
Sixth Street--Old buildings, college kids, bars and plenty of the unexpected.
Lots of new construction going on in downtown.
Congress Ave. and other streets with old and new buildings.
Enchanted Rock State Natural Area is a couple or three hours to the west. If you have the time this is a great place, but not on the weekends--too many people. Same pink granite as the capital building.
UT has some interesting architecture with great detail in some of the older buildings on campass.
I am sure that I have left out a bunch of stuff.