Duncan's Dam
The 928th tallest dam in the world
Duncan's Dam is a dam situated in Lisburn, County Antrim, Northern Ireland, near the Thiepval Army Barracks. It was used until 1941 as a water supply for Lisburn. The dam is now open to the public - there is a path around the water and a playground at the north end. The parking is free.
Dam data from Wikidata (CC0) plus curated additions. Summary from Wikipedia (CC BY-SA).