Peter and Paul Cathedral, of course, is the most valuable architectural monument, one of the spiritual symbol of Kazan. Built on an elevated site, a beautiful and majestic, cathedral differs by its kind of decoration. Composition of temple and bell tower is made in the style of the so-called Russian, or «Naryshinsky», Baroque, widespread in Russia at the end of XVII — the first half of XVIII century. This composition is also found in the Kazan region (Pyatnitskaya church in Kazan, the Church in Potaniha of Vysokogorsky area, both churches were built with funds of merchant Mihlyaev). Decor gives the unique appearance to the cathedral — an abundance of facade details and their bright coloring, which is preserved to our time. Unfortunately, the names of the builders of the cathedral remained unknown. Many art critics point to the similarity of decor with ornamental decoration of temples, built in the first half of XVIII century in the Ukraine. Perhaps the church is really was built by the Little Russians, but Peter and Paul Cathedral is not a simple mechanical copy of a style. Much of his appearance is unique and is the result of outside the stylistic predilections. Great merit for that, Kazan remained a magnificent temple, belongs not only to the builders of the cathedral and I.A. Mihlyaev, but the cathedral elders and the clergy later.
The fact that the temple was subjected to partial destruction. It was damaged during a fire in 1742, 1749, 1774 (with Pugachev), 1815, 1842″s. Particularly hard hit cathedral in 1815, when nine years of the parish moved into Gostinodvorskaya church. In the 1824-1825 years it was renovated by the means of the cathedral elders, Kazan merchant Sawa Stepanovich Zaitsev (grandfather of the outstanding scientist-chemist Aleksandr Mikhailovich Zaitsev). Since 1841 nearly a century elders were elected representatives of the merchant family Unzheninyh. In 1840 — 1850-ies. it was Vasily Unzhenin, in 1860 — his cousin Vasily Stepanovich Unzhenin, 1870-1880 — son of Vasily Stepanovich Peter Vasilyevich Unzhenin, since 1891 — his son Vasily Petrovich Unzhenin, who even when he found himself in exile in China up to 1929 sent large sums for the maintenance of the temple. For 1880 years the cathedral very dilapidated, the main cause of this was the destruction of the basement, and the belfry began to heel. Many details of decor lost the original appearance. Warden P.V. Unzhenin and dean Rev. Peter Vasilyevich Malov organized major reconstruction of the temple in 1888-1890. A young architect Michael Nilovich Litvinov made the project and directed the work (later in late XIX — early XX centuries he was the architect of the Cathedral of Christ the Savior in Moscow). Litvinov meticulously restored the original look of the cathedral. In this he was helped by detailed drawings and blueprints, which were made by the architect A.K. Schmidt in 1815.