My last big excitement of my trip to St. Pete was my visit to the Hermitage museum. It was an organized tour, which had its plusses and minuses. Plus: I wasn't afraid of getting mugged. Minus: I didn't get to choose what we got to see. We spent about an hour on the Winter Palace (cool), an hour on the treasures of the czars (yawn, and they didn't let us take pictures), and an hour on pre-18th century art (cool, although I was more interested in the rooms of Matisses and Picassos that they reportedly have).
The very distinct Russian Baroque style was similar to that of Peterhof.
They had a number of paintings by Rembrandt.
They also have two of the approximately 18 existing Da Vinci paintings.
The room containing them was very popular.
Here's a sculpture by Michaelangelo.
And of course, here's the final entry in my "Big Head Trilogy".