79

On 24 August 79, the Tenth Doctor caused Mount Vesuvius to erupt, killing thousands of Pompeii's residents as well as the invading Pyroviles when faced with the alternative of the Pyroviles turning Earth into a molten wasteland and erasing humankind's extant future. He had no choice but to let this happen, well aware he was creating a fixed point in time which would be forever ingrained in human history. Donna Noble shared the burden of setting off the eruption with him, knowing what effect this would have on the Doctor if he committed the act alone. Thanks to Donna's pleading, he saved one of the town's families, the Caecilius family. (TV: The Fires of Pompeii)

The Seventh Doctor and Melanie Bush likewise arrived in Pompeii and witnessed the eruption of Mount Vesuvius, but the Doctor remained completely ignorant of the presence of both his future self and the Pyroviles in the city. (AUDIO: The Fires of Vulcan)

Multiple visits were made by the 51st century ex-Time Agent and con artist Jack Harkness. (TV: The Empty Child / The Doctor Dances)

A time disruption briefly changed history so that Vesuvius took longer to erupt, allowing the city's populace to evacuate in their boats. (PROSE: The Algebra of Ice)

The Daleks once stole the Mark One model of a time machine called the Time-Conveyor, which was built by Peter and David's uncle. They hoped to reverse-engineer their own time machine from it. Peter and David pursued them through time in the Mark Two. They finally recovered it in Pompeii during the eruption of Vesuvius, having defeated the Daleks one-by-one along the way. (PROSE: Timechase)

Behind the scenes
One possible "game over" for the video game Don't Blink has the player being sent back in time by a Weeping Angel to the year 79 to die in Pompeii.