Orecchio di Dionisio
The Ear of Dionysius (Italian: Orecchio di Dionisio) is an artificial limestone cave carved out of the Temenites hill in the city of Syracuse, on the island of Sicily in Italy. Its name comes from its similarity in shape to the human ear.
The name of the cave was coined in 1586 by the painter Caravaggio. It refers to the tyrant Dionysius I of Syracuse. According to legend (possibly one created by Caravaggio), Dionysius used the cave as a prison for political dissidents, and by means of the perfect acoustics eavesdropped on the plans and secrets of his captives. Another more gruesome legend claims that Dionysius carved the cave in its shape so that it would amplify the screams of prisoners being tortured in it. Unfortunately, the sound focusing effect can no longer be heard because access to the focal point is no longer possible.
Because of its reputation for acoustic flawlessness, the Ear of Dionysius has also come to refer to a type of ear trumpet that has a flexible tube. The term 'Ear of Dionysius' can also refer to surveillance, specifically that for political gain.
There is a strong possibility that this feature is actually of natural origin. It lies on the down slope side of a substantial hill it could well be a 'slot' canyon cut by rainwater run-off in prehistoric times. Comparing it to other 'slot' canyons, especially those in the state of Utah (USA), it shows many similar characteristics. The narrowness of the top opening and widening of the lower part are also common to slot caverns elsewhere, as is its serpentine shape. The highly polished sides also suggest that the phenomenon was created by water. Such a natural feature, especially given its acoustics, would have been valued in the ancient world for its supposed sacred properties and this could have led to its preservation. Had it been man-made, why would the 'quarriers' bother to polish its walls to such a high degree, or remove stone in such an impractical fashion? Given that the building of the extensive Necropolis that abuts it on the hillside above involved removing a huge amount of the original overlaying rock, it is also possible that this 'canyon' extended even further before men began quarrying there.