Pompeii

Pompeii is a city in Italy. A group of Pyrovile landed in the region and slept for millions of years until awakened by an earthquake in 62 AD. At this point they set in motion a plan to terraform the earth into a planet of fire, so it could become their new world.

In 79 AD, the doctor arrived, and foiled their plan. Unfortunately, while this saved the Earth, it also triggered a catastrophic eruption of the Volcano known as Mount Vesuvius. The eruption completely destroyed the city and killed most of its population, 20,000 people. The eruption was so powerful that it briefly created a time rift, which by echoing back in time granted a number of citizens precognitive powers.

This event was according to the doctor a crucial and unchangeable event in history. Jack Harkness in his rogue days also claimed it was an excellent setting for a con job.

Eventully the city was rediscovered and Humanity remembered its faith. (DW: The Fires of Pompeii)