OT - HELVOETSLUIS, a fortified seaport in the province of South Holland, the kingdom of Holland, on the south side of the island of Voorne-and-Putten, on the sea-arm known as the Haringvliet, 52 m. S. of Brielle. It has daily steamboat connexion with Rotterdam by the Voornsche canal. Pop. (1900), 4152. Hellevoetsluis is an important naval station, and possesses a naval arsenal, dry and wet docks, wharves and a naval college for engineers. Among the public buildings are the communal chambers, a Reformed church (1661), a Roman Catholic church and a synagogue.