The Märcani Mosque, locally known as Möxämmädiä, is the oldest surviving stone mosque in Kazan and the only one to function continuously through the Soviet era. The exterior is unassuming — a low rectangular hall with a single minaret rising from the southwest corner — but its place in Tatar Muslim history makes it one of the city's most significant religious sites.
The interior, restored in the 1990s, has a calm green-and-white prayer hall. Visitors are welcome outside prayer times, with the usual rules about head covering for women. The mosque sits at the heart of the Old Tatar Quarter, near Lake Kaban.