If you are interested in art - and can drag yourself away from the
Hermitage - then the Russian Art Museum in St Petersburg is most interesting
and pretty well tourist free. (That won't be the correct name but I am away
from my office and can't check my records. I should think it would be
relatively easy to identify but if not, let me know and I will follow up.)
There is also an Ethnographic Museum that has much of interest, not that
you want to spend all your brief time in galleries and museums, of course -
but just some options to consider.
As with most special cities, walking is a pleasure in itself and the
streetscapes are uniquely beautiful.
The city has also an amazing collection of music and dance venues, so if the
opportunity arises for a performance, take it. You are unlikely to be