When Mount Vesuvius erupted in 79AD, Pompeii was not the only place buried under ash and pumice. Herculaneum was a town even closer to the volcano, to the west, and as a result was buried much deeper. Much like Pompeii, buildings and victims alike were extremely well preserved.
Excavation began in 1738, but remains incomplete. Today, the archaeological site is striking for the relatively modern-day buildings, themselves dating back to medieval times, almost stacked on top of the Roman ruins. Excavation has presently halted so that funds may be diverted to the survival of Ercolano, the current town.
It remains open to the public, though tourists may gradually be damaging the accessible ruins.