The main structure of the ensemble is the Epiphany Cathedral, which consists of "old" and "new" parts. In 1982, a fire occurred in the cathedral, almost completely destroying its frescoes. From 1985 to 1991, the building was restored by the KSNRPM. The "old" cathedral, a beautiful example of monastic architecture from the mid-16th century, was created by Rostov masters and is distinguished by its monumentality and impressive forms. It is a typical cross-domed building of that time with four pillars, five domes, and three apses, built on a high stylobate. Its large two-light square, originally covered with zakomara, is topped with onion-shaped domes on large cylindrical drums. The power of the cathedral's forms is especially noticeable from the east, where the strong semicircles of the apses stand out, separated by rectangular columns. Wide pilasters divide the cathedral's facades into three bays, visible from the upper part due to the extensions, and are completed with keel-shaped zakomara. The entablature, supported on the pilasters, separates the zakomara from the walls. In the middle bays, inside the extensions from the south and north, there are preserved perspective portals with white stone details; the previous windows have been bricked up or enlarged. The drums of the domes are decorated with arcature on columns and a belt of small towns under the cornice. In the interior of the cathedral, powerful cross-shaped columns are widely spaced and support the barrel vaults of the cross arms with the help of spring arches. The sails provide a transition to the drums above the central and corner cells with eight windows in the central and four in the side ones, with the main spring arches above the vaults. The apses, fully open to the temple, with the southern one housing the Assumption chapel, are covered with barrel vaults with conchs. An internal staircase in the southern wall leads to the vaults. In the vaulted stylobate, there was a burial vault with tombstones from the 16th to 18th centuries, where the boyars Saltykov, Prince I. Khovansky with his family, Boyar A. Kaftyrev, and the abbots Isaiah and Gerasim, among others, were buried.

Before the fire in 1982, the interior of the cathedral preserved frescoes created between 1667 and 1672 "by the efforts and diligence of Abbot Gerasim." This was one of the early works of Kostroma icon painters under the guidance of Guriy Nikitin. In 1865, the frescoes were completely repainted by Palekh artists from the Safonov artel using the old grafia. The frescoes of the cathedral before the fire were studied by V.G. Bryusova, and their iconographic composition was described in detail in her monograph "Guriy Nikitin," where the author suggested that the frescoes of the upper parts of the cathedral were created in the 16th century. However, the complete identity of the plaster base of the "upper parts" and the walls of the square, established as a result of chemical analysis conducted during the restoration of the building, does not confirm this assumption. After the fire, separate fragments of the plaster base remained in the square, the grafia was visible, but the paint layer had burned out and was washed away by water. During the restoration of the cathedral, new plaster was applied in the places of loss, and the entire interior was whitewashed. In the stylobate of the cathedral, where the burial vault was located, frescoes from 1672 have partially survived despite the water intrusion.