Lagan Weir is a significant structure located on the River Lagan in Belfast, Northern Ireland. It was completed in 1970 and serves to regulate the river's flow, helping to manage water levels and prevent flooding in the surrounding areas. The weir also plays a role in improving navigation for boats traveling along the river. The structure features a series of sluice gates that can be opened or closed to control the water flow. In addition to its practical functions, Lagan Weir is a popular spot for local residents and visitors, offering scenic views and recreational opportunities along the riverbank.