Thank you Alexander! The top right 2005 stamp shows Chersonesus Taurica, the ancient Greek city in Sevastopol. The Russian government undertook the first excavation here in 1827.  
Thank you Veronika who sent this postcard of it!
Thank you Alexander! 2013 'Sevastopol Cathedral' stamps with Chersonesus on the selvage.
Thank you Lena! Russian s/s titled: World Heritage: The Ancient City of Tauric Chersonese and its Chora. This has been mailed on a first day envelope. Stamp issue date: October 23 2015