Mount Vesuvius erupted in AD 79 killing inhabitants from the heat emanating from the volcanic explosion. Tephra poured down for about 6 hours covering the people and buildings of Pompeii in up to twelve layers. The cities were soon abandoned and forgotten until 1599 when part of them were unearthed in digging an underground channel. The sexually explicit frescoes were recovered in an act of censorship. It was not until 1738 that Herculaneum was properly rediscovered and excavations began.