Pompeii was an ancient Roman city in Italy that was buried under ash and stone when Mount Vesuvius erupted in 79 AD. Archaeologists later excavated the site and discovered that the volcanic debris had preserved the city, including people and objects in the positions they were in when the volcano exploded. The documentary provides an overview of what can be seen on a one-day tour of Pompeii's ruins, including preserved structures and artifacts that give insights into daily Roman life before the city's destruction.