In 1479 a stronghold was built on the isle in the middle of Lake Porkuni, but it was destroyed a long time ago, during the Livonian War (1558-1583). Only the barbican remained. To maintain the barbican, that has belonged to the estate for centuries it has been reconditioned.
After the WW2 the barbican belonged to Porkuni school. For the quincentennial of the barbican it was reconditioned and taken into usage as a common room of the school. In 1991 an exposition about the history of teaching deaf people in Estonia was compiled here. From June 4, 1992 the limestone exposition was added.
Visitors get a comprehensive overview of limestone – Estonian national stone all through the five storeys of the barbican tower. Exposition introduces the formation story, distribution and use of limestone and various zoolites. There is also elaborate collection of limestone samples throughout Estonia. In the top of the barbican there is an observation platform. From here one can take a glance at the complex of manor buildings, Lake Porkuni and the surrounds.
Limestone museum is also convenient place for high school and college students to acquire additional knowledge about geology. Hobbyists can investigate and manipulate limestone samples on their own, also define and determine the zoolites. Local guides are giving relevant information about the exposition and sites of cultural heritage in Porkuni.
Porkuni Limestone museum is administered by Tamsalu commune.