In Naples’ Sanità district, mopeds hurtle along cobbled streets dotted with larger-than-life markets as locals and visitors alike form around-the-block lines for some of the world’s best pizza.

Some 2,000 years ago, this lively Naples neighborhood was a very different place. Situated just outside the walls of Neapolis—the Greek city so respected that even under the Romans, its Hellenistic culture was allowed to flourish—it was once a hilly area composed of volcanic tuff rock.