The crypt is the oldest part of the Grossmünster. Its murals from the 14th/15th century have faded considerably. Attributed to Hans Leu the Elder, they depict the martyrdom of the patron saints Felix and Regula. You can also view the original statue of Charlemagne from the southern tower.
In the remainder of the former Chapel of the Twelve Apostles, remnants of the frescoes are visible and you can admire a model of the original construction of Grossmünster. Part of the oldest Zurich cityscape by Hans Leu the Elder has been recovered from the former decor of the Chapel of the Twelve Apostles. The panels had been reduced and partly repaint, because the scenes from the martyrdom of the city patrons did not seem of interest anymore after the Reformation.
Source: Sidonius / Wikipedia (↗ entire authorship attribution)
Summer | 1 March – 31 October
Mon–Sun, 10 am – 6 pm
Winter | 1 November – 28 February
Mon–Sun, 10 am – 5 pm
Admission free of charge