Architecturally, this abbey is a marvel of the early Romanesque style, specifically designed to handle the extreme slope of the mountain. Because there was so little flat ground, the architects built a unique double church—one literally stacked on top of the other. The lower church, often called the crypt, is a mysterious, subterranean world dedicated to the Virgin Mary. Its low, rounded vaulting and heavy pillars create a heavy, earthbound atmosphere that feels centuries older than the light-filled valleys outside. In contrast, the upper church, dedicated to Saint Martin, features a narrow nave just 3 meters wide. This slim, vertical design was a cutting-edge experiment in barrel vaulting for its time. Notice the capitals—the tops of the columns—which are some of the earliest examples of Romanesque stone carving in the region. Here is a practical tip for you: as you explore, look for the small windows. Because windows weakened the walls that held up the heavy stone roof, they are tiny, meaning the interior is often bathed in a soft, contemplative twilight.