I love Markarth. The architecture is my favorite of any environment I've encountered in the game yet, and I want to buy Vlindrel Hall in the city since it seems like a worthy purchase. Unfortunately though, the bug with it means I can't, so I am hoping it is addressed in a patch.
Standing outside Vlindrel Hall and looking down to the city below is something that makes me really happy about the game design. Markarth reminds me a little of Fallout 3's Megaton with the different tiers of the city, but it's a much more elegant looking city.
I haven't yet looked out from the Dark Brotherhood Sanctuary but the next time I'm at it I'm going to remember to take a look, since I imagine the environment will be fantastic looking. Markarth remains my favorite location in Skyrim at the moment but if I see something really amazing it could be topped.