Sri Lanka, Sept. 3 -- A remarkable piece of 17th-century engineering beneath Sri Lanka's historic Galle Fort is receiving renewed attention as authorities begin cleaning and restoring its underground drainage network.

Built during the Dutch colonial era, the system is considered one of the fort's most sophisticated examples of early urban engineering, combining sewage disposal and rainwater management with a design that made use of the natural movement of the sea.

The underground network was constructed with black stone and bricks in a strong arched structure, designed to withstand the demands of the coastal environment.

What makes the system particularly remarkable is the way it was engineered to regulate itself. According to official...