This impressive cathedral is affectionately known to English speakers as the "Gross Monster." Executed on the plump twin towers (circa 1781) are classical caricatures of Gothic forms bordering on the comical. The core of the structure was built in the 12th century on the site of a Carolingian church dedicated to the memory of martyrs Felix and Regula, who allegedly carried their severed heads to the spot. Charlemagne is said to have founded the church after his horse stumbled
over their burial site. On the side of the south tower an enormous stone Charlemagne sits enthroned; the original statue, carved in the late-15th century, is protected in the crypt. In keeping with what the 16th-century reformer Zwingli preached from the Grossmünster's pulpit, the interior is spare, even forbidding, with all luxurious ornamentation long since stripped away. The only artistic touches are modern: stained-glass windows in the choir by Augusto Giacometti, in the western nave by Sigmar Polke, and ornate bronze doors in the north and south portals dating from the late 1940s.