There is no volcano that buried all of Italy. Italy has many volcanoes, but none of them have ever erupted with enough force to bury the entire country.

It's possible you're thinking of the eruption of Mount Vesuvius in 79 AD, which buried the Roman cities of Pompeii and Herculaneum in ash and pumice. While this was a devastating event, it only affected a small area of Italy.

Do you have any other information about the volcano you're thinking of? Perhaps the specific location or the type of eruption?