I received two cards from Kiev, Ukraine, showing similar but not the same churches:
This card comes from lazy_rabbit. It shows the Architectural ensemble of Mykhailivskyy, which according to the card was rebuilt in 1999 after originally being built in the 12th century.
The next card was an official Postcrossing card from a student named Oksana:
This is Saint Sophia’s Cathedral, which has been on the UNESCO list since 1990. Work started on the cathedral in the 11th century. The cathedral is named after the Hagia Sophia in Istanbul, not after a particular saint named Sophia. The cathedral was the burial place for the Kievan rulers.
Oksana used very nice stamps on this card:
I like the triangular one best of all, because I like non-rectilinear stamps.