Dante,
There are several wedding palaces in St. Petersburg:
One that was at Petrovskaya Embankement No. 2, was the palace of Grand Duke Nicholas Nicholaevitch. It has been taken over for the use (I believe) of President Putin.
Another wedding palace is at English (Anglisky) Embankment, No. 28. It was built for the Baron von Derviz and was later owned by Grand Duke Andrey Vladimorovich who lived there with his lover Matilda Kshesinskaya before he built her house on Petrogradskaya.
Another House of Weddings that I think is still at Furshtadskaya, No 52 which was owned by Count Paul Nicholaevitch Ignatiev. It had also be used as the Spanish Embassy.
There may be others, but I'm not aware of them.
BobG