Kalbosu is a prison built by the Portuguese troops around 1925/1930. It was built by two white men, Lopes and Kurubelu. They built this prison because at that time there was no prison in Suai. The prison was built for robberies and theft and other criminals.

The prison can feed up to ten people. The prisoners were only kept there at night time and during the day the government sent them to Audian to clean garden.

When the Japanese occupied East Timor during the Second World War, the Japanese also kept the Timorese prisoners at Kalbosu. There was a story of a man who managed to escape from Kalbosu. His name is Nahak Lu. Nahak Lu was asked by the Japanese to do fishing during the day. One day Nahak Lu instead of returning to Kalbosu with fish he ran away to Betun and never returned to Suai since. He remarried in Betun and died there and left a son in Suai Kamansa.