Late in the year 79 CE, the citizens of Pompeii and Herculaneum would have found this question extremely pressing. When the nearby stratovolcano Mount Vesuvius erupted, it set off a cycle of chaos that wiped out both towns and their citizens.
The eruption began on August 24th and completed on August 25th with no trace of Pompeii left. The river and port were gone. Within a few years no one could remember where the city once stood.