Among the surviving structures of the monastery, built in the 16th and 19th centuries, special attention is drawn to the Transfiguration Cathedral. According to legend, it was built with the funds of Ivan the Terrible after the victory over Kazan in 1552 on the site of an old wooden church of the Savior. However, there are no documentary confirmations of Ivan the Terrible's involvement in the construction of the cathedral, although the 1624 inventory of Kireevsky mentions that "the monastery and churches and icons and candles and books and vestments and bells and all the monastic buildings belong to the Sovereign."

The architecture of the 16th-century cathedral suffered significantly during the annexation in 1839 and restoration at the end of the 19th century, but most of the architectural details from the 16th century were restored, allowing the Transfiguration Cathedral to largely retain its original forms.

Like the Nativity Cathedral, the Transfiguration Cathedral is five-domed, four-pillar, and single-story. Since the Spassky Monastery served as a fortress on the approaches to Murom, the architecture of the cathedral is characterized by severity and monumentality, while the details are marked by conciseness and clarity. The cathedral's domes have a distinctive silhouette, with bulbous heads characteristic of the 17th century installed at the tops of the domes. Restoring the 16th-century domes in a helmet shape is not difficult. Currently, the Transfiguration Cathedral of the Spassky Monastery is the only fully preserved monumental structure from the 16th century in Murom, as most buildings from that time have been lost, including the Annunciation and Nativity Cathedrals, the Nikolai-Mozhaisk Church, and others. The old Kozmodemyansk Church has been in a semi-ruined state for almost 100 years, since 1868.

The cathedral building is almost cubic in volume and square in plan, located in the center of the monastery at the intersection of longitudinal and transverse axes. It is distinguished by its austere simplicity and conciseness of architectural forms. The western, southern, and northern facades are divided by flat pilasters into three parts, emphasizing the division of the internal space, which is separated by four square columns into three naves. Semi-circular zakomars in the form of kokoshniks rest on a wide cornice made of several rows of bricks set on edge.

The cathedral is topped with five domes, the drums of which rest on keel-shaped kokoshniks, and a cornice made of a double row of brick teeth. The drums have slit windows that illuminate the interior of the temple. Although the bulbous heads of the 17th century slightly alter the original architecture of the building, the drums of which were likely covered with helmet-shaped domes, the Transfiguration Cathedral retains its monumentality and severity. Like many cult buildings of the 16th century, the cathedral served as a fortress, acting as a storage place for valuables and a refuge for residents during sieges.