Just to the north of Pi Leh Bay is the Viking Cave where swifts make their nests. There are some paintings on the walls of boats resembling Viking ships that are supposed to be ancient however they're more likely to be just a couple of hundred years old… if that. However, the Viking tag has stuck.
The nests are made by the birds from their saliva and harvested from February to April by locals who use rickety bamboo scaffolding to get up to them once the birds have finished nesting. The nests sell for many thousands of Euros per kilo and are used for the Chinese delicacy bird’s nest soup.