This unusual underground church, the largest in Europe to have been built "from a single stone" was constructed in the rock in the late 11C. The interior is impressive, both for the sheer scale of the naves carved deeply into the rock and for the perfectly regular cut of the arches and four-sided pillars. The bell tower, built between the 12C and 16C, is dotted with Romanesque windows and crowned with a 15C spire. It is well worth climbing the 196 steps to admire the views from the top!