I was very impressed with St Basil's, but the light outside was flat and boring so I added some contrast and punch by taking 3 bracketed exposures and using Photomatix.
The last shot I used the 50mm f/1.2 wide open - partly because of the low light levels inside and partly because I wanted a very thin dof.
Canon EOS-1Ds Mark III, f/3.5 @ 24 mm, ISO 100
Canon EOS-1Ds Mark III, f/2.8 @ 50 mm, ISO 100
Canon EOS-1Ds Mark III, f/1.2 @ 50 mm, 1/20, ISO 400, No Flash