Church of Saint Boris and Saint Gleb (official name - the Cathedral of the Holy Martyrs, princes Boris and Gleb) - a monument of Gothic architecture of the Grand Duchy of Lithuania of the XVI century. It belongs to the temples, adapted for defense.
Church was built in 1519 on the site of an ancient temple of the XII century. Fragments of its foundation were found during excavations in the 1960s. This temple was a cathedral of the Lithuanian Mitropolia with the  male monastery. In 1451 temple was visited by prelate Jonah, Metropolitan of Moscow and all Rus.
In 1517 on the site of this ancient temple brick church began to build at the expense of the magnates - Hetman Constantine Ostrogski and Metropolitan Joseph Soltan.
In 1620 church was transferred to the Uniates. Few years later Metropolitan Josef Ruckiy create Basilian friary and convent. In the period from 1624 to 1632 the church was rebuilt in Sarmatian Baroque style at the expense of local magnate Alexandr Hreptovich. Towers with loopholes appears On the facade appears towers with loopholes and spiral staircases inside the temple and because of this temple gained a warlike look. 
In 1839 the church was transferred to orthodox. At the end of the XIX century the church was reconstructed again. The building acquired features of Russian architecture.
In the middle of the XX century the church was closed, and the building was used as an archive. Only in 1996 the church was returned to the Orthodox.
Church of Saint Boris and Saint Gleb – a striking example of the Orthodox Gothic in Grand Duchy of Lithuania of the XVI century. Originally it was a three-nave temple with four pillars and pentagonal apse. Towers on the facade were added later during the Renaissance restructuring. Architecturally this church is very simmilar to the early Catholic churches of the Principality, but felt the powerful influence of the Orthodox-Byzantine tradition because of facade designe and Gothic elements.