The Catherine Palace at Tsarskoye Selo. A huge palace in the Baroque style. Personally I don't like the place much (been there twice now), the only thing that is worth a visit for me is fall colors combined with the golden domes on the chapel.
Unfortunately the weather was bad, the chapel and garden were being renovated and they were shooting a movie (and therefore kicked everyone out).

So, not a lot of photos from this place, sorry.