The first buildings to be built in Friesland using natural stone or bricks were stone refuge towers, known in Friesland as ‘stinzen’. ‘Stins’ means stone. These squat towers with rounded peaks served as a refuge for their owners, the farming gentry. These people were the rural aristocracy in Friesland, which had no earls or counts before 1500. http://www.leeuwardenholland.nl/en/

Saint Peter’s Fortress was built on St. Peter’s Mount in the early 18th century. It’s initial purpose was military, allowing the people of Maastricht to defend the city from the French. While successful for a long time, the city had to surrender in the end. https://www.holland.com/global/tourism/destinations/maastricht/fort-st-pieter.htm