The Basilica di San Francesco is one of the main religious buildings in the town of Ascoli Piceno located in central Italy. Considered the finest example of Franciscan architecture in the region of Marche, the main entrance of this church contains a unique feature. 

The entrance is located along a narrow alley on the side of Piazza del Popolo, the main square of Ascoli Piceno. On each side of the large central door, five thin pillars decorate the entrance and also happen to be hollow inside. Each pillar contains a small hole of varying dimensions, making the columns similar to organ pipes. Knocking on the pillars will produce several different sounds.

Over the years, locals and tourists have come to this spot to knock on the columns with metal objects to hear their melodic tune. The effects of centuries of knocking can be seen across the pillars, as a few have notable signs of wear. Today using objects to hit the columns is prohibited, but you can still knock on them with your hands to hear their curious sounds.