Before the devastating eruption of 79 AD, the inhabitants of Pompeii had no idea they lived beside a volcano since it hadn’t erupted in around 1,800 years. In comparison, it’s been very active since, having erupted 6 times in the 18th-century, 8 times in the 19th-century and 3 times in the 20th-century. It last erupted in 1944.
When the volcano does eventually erupt again, it has the potential to be massive, affecting over 3 million people and destroying the city of Naples.