Fa hien caves basking on the kalutara district are the oldest evidences for Mesolithic habitation in Sri Lanka. The cave gets the name due to the visit by the Buddhist monk and the explorer 'Fa hieyn' to ancient caves in 399 A.D. Thero 'Fa hien' was at residency for a while on his journey to the Adams peak. These are concerned as the largest cave complex in sri lanka.
In addition you have to go for the Yatagampitiya village near the Bulathsinhala town of kalutara to see the caves. The cliff face where the caves are positioned is marvelous. So that, it is witnessed through the Radiocarbon examines hat they are now 33000- 4750 years old.