Ancient constructions of Sri Lanka
The ancient Sinhalese excelled in the construction of tanks (Wevas) or reservoirs, dagobas (or stupas), and palaces in Sri Lanka, as evident from the ruins which displays a rich variety of architectural forms. == Irrigation works == Major irrigation schemes of Sri Lanka, as evident from the earliest written records in the Mahawansa, date back to the fourth century BCE (Parker, 1881; Brohier, 1934).
Source: Wikipedia — Ancient constructions of Sri Lanka (CC BY-SA 4.0)