This extraordinary group of more than 20 metres of underground galleries once formed part of the water system designed by Roman engineers in the 1C AD. Although the site was discovered in 1969, excavation did not start here until 1991. The site offers a glimpse of a typical Roman sewerage system with a main channel covered by a barrel-vaulted ceiling and the original terracotta flooring into which water from other galleries would be channelled. A series of cryptoporticos has also been excavated on the same site.