A сornerstone is a large first stone set into the future construction foundation. The Radogoshch Museum houses a сornerstone, set into the foundation of the Assumption Cathedral with a side-chapel in the name of the Intercession of the Theotokos in the town of Pogar in the late 18th century. There is a square hollow in the upper part of the stone with a Cossack cross carved in its center.

At various times, the copper plaques blessing the construction of the church were placed in this niche. There was an inscription on one of those plaques,

The Chernigov and Novhorod-Siversky bishop, who blessed the construction of the side-chapel, as well as priests, sotniks, and benefactors, were also mentioned in the text. The date of the сornerstone setting “the month of June 2nd, 1764” was indicated on the plaque. Later another text was fitted there,

Further, the names of knyazhs and churchmen, involved in the construction of the church were referred to. This plate was installed later, in “the first days of June” of 1791.

The Assumption Cathedral in Pogar already existed by the time Ukrainian lands joined Russia in 1654. At that time, it was a wooden church located inside the city fortress. In 1684, the Assumption Cathedral was built in the other location, outside the fortress on the money of the Starodubsky Regiment colonel’s wife Maria Samoylovich. She donated land and money for the Cathedral and its small shops. In the church, there were side-chapels in the name of St. John the Evangelist and Antoniya and Theodosius of the Kuiv Caves in addition to the Dormition of the Mother of God’s high altar. The Cathedral’s warm church (for winter services) was dedicated to the Intercession of the Blessed Virgin Mary.

On the night of August 28, 1801, the Assumption Cathedral burned down. Emperor Alexander I granted 2,000 silver rubles for a new stone church construction. The new church was consecrated in 1819. The dome was 27 meters high and the bell tower was about 30 meters. During the Great Patriotic War, Red Armymen were held captive there by the Nazis. In 1960, the church was demolished.