Short answers, pulled from the story.
Ivan the Terrible ordered the rebuilding of the Kazan Kremlin on the ruins of a former castle belonging to the Kazan khans. This massive project began in the 16th century and relied heavily on local materials.
The Annunciation Cathedral dates from 1554 to 1562 and stands as the oldest surviving structure within the complex. It remains unique among 16th-century Russian churches for its six piers and five apses.
Soviet authorities pulled down that bell tower in 1930 after it had been erected in five tiers at the urging of Ivan the Terrible. The Communists also destroyed the buildings belonging to the Spassky Monastery during Joseph Stalin's rule.
The opening of the new mosque occurred on the 24th of June 2005, with roughly 17,000 people gathering for the celebration. Delegations from forty countries attended the event.
The most conspicuous landmark of the site is the leaning Söyembikä Tower which likely dates back to the reign of Peter the Great. A well-known legend connects this tower with the last queen of the Khanate of Kazan.