Complex sentence: The original icon was kept in the Theotokos Monastery of Kazan (built to commemorate the spot where it had been discovered), whereas several ancient and venerated copies have been displayed at the Kazan Cathedral of Moscow, at Yaroslavl, and at St. Petersburg.
Split into simpler sentences: The original icon was kept in the Theotokos Monastery of Kazan (built to commemorate the spot where it had been discovered). Other churches were built in honour of the revelation of the Virgin of Kazan and copies of the image displayed at the Kazan Cathedral of Moscow, at Yaroslavl, and at St. Petersburg.