Holy Trinity church, Orthodox church in Nevsky District, Saint Petersburg, Russia

The Holy Trinity Church consists of a round rotunda with sixteen Ionic columns and a low green dome, joined on the left to a lower rectangular wing with a green roof and arched dormer windows. Behind the wing rises a white bell tower with a pointed spire and cross. The bell tower is a four-sided metal-clad pyramid, not a dome: its lower tier holds a baptistery, its upper tier the bells, and small painted clock faces show different times on each wall.

Nikolay Lvov designed the church for General-Prosecutor Alexander Vyazemsky, owner of the village of Alexandrovskoye, and it was built in 1785–1790. In 1858 a vestibule was added at the entrance and a small porch at the altar end to enlarge the space for parish services. Admiral Alexander Kolchak was baptised here on 15 December 1874; the parish register records his parents as staff-captain Vasily Kolchak and Olga Ilyinichna.

The name comes from the shape of the complex: the round church stands for the kulich, the Easter bread, and the four-sided pyramid bell tower for the paskha, the triangular curd dish. Prince Alexander Vyazemsky, owner of the village of Alexandrovskoye, chose this design. The bell tower's pyramid follows the Pyramid of Cestius in Rome, which Lvov had studied on his Italian journey of 1781.

The church stands at 235 Obukhovskoy Oborony Avenue, on the left bank of the Neva in the Nevsky District, southeast of the historic centre. The entrance with its columned portico and gated door faces the avenue; the bell tower rises behind the left wing. The rotunda's lack of a drum keeps the altar side dim, so look up at the blue dome and the angels above the apse.

The bell tower reproduces the Pyramid of Cestius in Rome, an impression Lvov brought back from his Italian journey of 1781; the round church echoes the round temples of Vesta in Rome and Tivoli that he sketched there. Above the bell openings, small painted clock faces each show a different time.