The High Altar, inspired by a Roman design, was built of black-gray marble from a quarry in Stanserhorn. The white parts are alabaster, likewise taken from Central Switzerland. After its inception in 1639, the altar inspired awe in the faithful. To this day, no altar in the classical Roman Baroque tradition has been created north of the Alps. The altar picture with the scene from the Mount of Olives was painted by the Roman painter Giovanni Lanfranco.