It looks like the same building as the Blades temple in TES V Skyrim, which is also located in the Reach. Unfortunately, it's out of bounds according to UESP, so you can't go there.

We can even see it from the N Markarth wayshrine. If you look in the exact direction of the temple, you'll see what looks like a pointed temple roof, partly obscured by heavy mist. I also tried to get up there, but the mountainside is too steep.