The Spasskaya Tower, with its over‑gate Church of the Holy Mandylion, is the main entrance to the Kremlin and is located in the centre of the southern fortifications. It was built in 1556–1562 by Postnik Yakovlev and Ivan Shiryai. The church interior was originally intended to house Ivan the Terrible’s marching icon and other relics from the Russian assault on Kazan in 1552. The tower was originally two‑tiered, with a wooden hipped roof and a small watchtower. In the 1670s, the tower was heightened by two additional tiers with a hipped roof at the top. The two lower tiers (16th century) are four‑sided, white‑stone structures with an arched passageway. Two brick octagonal tiers (17th century) rest on them. The lower octagonal tier houses a clock, while the upper tier is pierced by arched openings forming a clock belfry. The tower is crowned by a brick hipped roof. The rectangular volume of the church adjoins the tower along its entire length, has a gable roof, and its façades retain 16th‑century decoration. The tower walls were 2.5 metres thick.
In the middle of the 19th century, a pointed arch was pierced in the section of the fortress wall adjoining the tower on the east side to make the main entrance to the Kremlin more convenient. The dog‑leg passage was removed by walling up the gateway. In the 1870s, an extension with a staircase leading directly into the church was built on the west side, thus completely isolating it from the tower. In 1930, a direct entrance for vehicles was created through the Spassky Gate. In 1963, the tower was fitted with an electric clock with dials on three faces of the octagon and automatic chiming, and a finial in the form of a five‑pointed star was added. The tower clock was fitted with special equipment: now, after dark, a crimson flash appears when the clock strikes.
Restoration work was carried out in 1957 and 1970–1975. Repair of the wooden structures and restoration of the white‑stone masonry were carried out under the supervision of architect S.S. Aidarov.