✅ Originally it was the lower floor of an older villa (a "basis villae"), which emperor Hadrian incorporated into his own. It was used to walk indoors and in one corner there was a small fountain: so it was used in the summer as a cool and sheltered place.

✅ In this Cryptoporticus an extraordinary mosaic ceiling is preserved almost intact. It is decorated with shells, colored tesserae and glass paste sticks. It dates back to the II-I century BC, and it is unique in the world because it is still on site.

✅ The Cryptoporticus is illustrated in some 19th century engravings, including those by Agostino Penna. It still gets light from some window-tunnels that open in it upper part of the vault. It was entered from the Hospitalia, and two internal stairs went up to the upper floor of the Imperial Palace.

✅ The Cryptoporticus communicated with a series of subterranean corridors that led into the hill: they still have to be explored. Unfortunately it was closed to the public more than twenty years ago, although the ceiling was recently cleaned and restored.

‼️ A precious ceiling, unique in the world!

See also my book Villa Adriana Mosaici Pavimenti Edifici, pp. 98-102 and 401-404.