The sprawling Mission Inn in Riverside, California was the dream of eccentric art collector Frank Miller. For over thirty years he salvaged and copied European architectural elements of questionable compatibility to create a complex unlike any other, although it’s often compared to a scaled down Hearst Castle.

Around 1915 Miller began creating a network of catacombs beneath the building to provide a comfortably cool space for guests to stroll and view artwork. The main passageway was designed to represent the Camino Real, the route linking the twenty one Mission settlements in early California. Oil paintings of each Mission by Henry Chapman Ford were displayed in niches along its walls.

After passing tableaus of biblical scenes, visitors reached the centerpiece of the catacombs, a waxworks display of Pope Benedict XV and members of his Papal Court. It was originally created for San Francisco’s 1915 Panama Pacific International Exhibition and came into Miller’s collection shortly thereafter. Apart from the rods that supported the figures in the semicircular room where they were staged, no trace of the delicate figures remains.

When new owners undertook the ambitious project of saving the crumbling Inn in the 1980s, they found countless bizarre treasures. A room off of the catacombs contained forty pianos, including an extremely rare 1876 Steinway built to commemorate the centennial. The piano had gone missing in Missouri in the 1920s, and how it came to Riverside remains a mystery. It has been restored and can be seen in the main lobby of the Inn.

It is generally believed that the catacombs once continued beyond the footprint of the building, though just how far is the subject of much local lore. Some dubious accounts claim there was once a passageway to Mount Rubidoux more than two miles away.

For safety reasons, the catacombs are now closed to the public.