Directly across from the Toompea , Castle is the imposing Alexander Nevsky Cathedral with its five onion domes. It was built here when Estonia was part of the Russian empire.The site was previously the site of a garden centered around a monument to Martin Luther. The building designed by St. Petersburg Art Academy professor M. Preobrazhensky is dedicated to I Alexander Nevsky Prince of Novgorod, whose victory on the ice of :Lake Peipus in 1242 halted the eastward advance of crusaders. The lavishly decorated cathedral features an amalgam of historical styles and is an example of Orthodox sacral architecture on a grand scale.The tower contains 11 massive bells-including Tallinn's largest, a 15-ton affair-which peal before services. The murals, the stained glass window in the east wall a three-part iconostasis and the mosaic in the facade are all worthy of note.
The Alexander Nevsky Cathedral is an operational Russian orthodox church.