This is it:
EUROPA (issued 15-03-2017)
The stamp shows the Saint Michael's Castle in Saint Petersburg. The Saint Michael's Castle was built between 1797 and 1801 as a residence for Emperor Paul I. It was built in a combination of French Classicism, Italian Renaissance and Gothic. Due to his fascination with medieval knights and his constant fear of assassination Paul I ordered the new royal residence to be built like a castle, but ironically he was killed in his own bedroom just 40 nights after he moved to his new residence. Today the Saint Michael's Castle houses the Portrait Gallery of the Russian Museum.
The stamp was sent in a FDC of the same stamp.
Thank You very much Elena!