Monstersche Sluis

The Monstersche Sluis was still only an air gap in the Maas dike in 1343. In 1602, the lock was rebuilt as a drainage sluice by order of the Municipality of Monster. During the 1889 restoration, the sluice was converted into a lock. Small (horticultural) ships were now able to pass from the canal to the port and vice versa. Coloured-in postcards give you an impression of Maassluis around 1900. The water levels in the Nieuwe Waterweg rose due to the Delta Works. As a result, the lock could practically no longer be used for sluicing. Also, not many ships were still moving through the locks. In 1972, the Provincial States of South Holland granted permission to close the Monstersche Sluis to shipping. On the flowing canal side of the lock, a clay cofferdam was installed to prevent salinisation of the basin by leakage of brackish water from the port. After 1972, only the visible parts of the lock were still maintained. On 1 September 2018, the historic lock was ceremoniously reopened. The official opening ceremony was performed by Jaap Smit, the (then) Queen's Commissioner for South Holland. The opening of the Monstersche Sluis offers water recreationists a whole new range of opportunities. Pleasure boats can now reach Maassluis' inner harbour from Midden-Delfland. Opening hours of the lock can be found here.