Fort Tienhoven
Fort Tienhoven, in the Tienhoven polder, was built in 1848–1850. The fort originally consisted of a defensible guardhouse, which was later converted into bomb-proof barracks. It served to close off the Tienhovense Vaart and guard the adjacent inundation quay, dam lock and Kraaienester lock. A cast-steel domed casemate housing a heavy machine gun was added in the interbullum to cover the Tienhovense Vaart and the quay. The fort has been reclaimed by nature. These days, its main purpose is as a roost for bats.