Fort Senneville Fort Senneville is one of the outlying forts of Montreal , Quebec , Canada , built by the Canadiens of New France near the Sainte - Anne rapids in 1671 . The property was part of a fief ceded to Dugué de Boisbriant in 1672 by the Sulpicians . A large stone windmill , which doubled as a watch tower , was built on a hill by late 1686 and featuring machicolation and other castle - like features . The fort was burned down by Iroquois in 1691 , with only the mill itself left standing . Governor - General Frontenac ordered the construction of a second , more imposing fort in 1692 . It was rebuilt in 1702 - 03 to protect the nearby fur trading post . With extensive cannon s and swiveling wall guns , it was the " most substantial castle - like fort " near Montreal . It was eventually destroyed in 1776 by Benedict Arnold , while under American military control , but the ruins have been maintained since then . In 2003 , it was classified as a historic site . Background . Thanks to the tireless work of French explorers , the colony of New France covered the largest area , but it was numerically inferior to the neighbouring New England . Consequently , a number of " Ingénieurs du Roi " ( " King ' s Engineers " ) were appointed to make the colony the best fortified in North America : Quebec served as the only fortified city in the Americas , centred around the Citadelle of Quebec . An unusual feature of Montreal ' s defence was a string of 30 outlying forts to protect against the constant Iroquois threat to the expansion of French settlements . The majority of these were simple stockades , but as artillery was not as developed as on the battlefields of Europe , some of these were built like the fortified manor houses of France . Roughly four of these were substantial stone forts which served as defensive residences , sometimes considered " true castles " , as well as imposing structures to prevent Iroquois incursions . Initially , Fort Senneville was a French stockaded fort , built in 1671 about half a mile above the Sainte - Anne rapids . The property was part of a fief ceded to Dugué de Boisbriant in 1672 by the Society of Saint - Sulpice , and subsequently relinquished in payment of a debt to two of the most significant figures in New France ' s history : Jacques Le Ber and Charles Le Moyne , who used the site as a fur - trading post . A large stone windmill was built on a hill by late 1686 , doubling as a watch tower over the Ottawa River , the Lake of Two Mountains and the mouth of the Des Prairies River . This windmill was like no other in New France ( although a similar fortified windmill was later built in Quebec ) , with thick walls , square loopholes for musket s , with machicolation at the top for pouring lethally hot liquids and rocks onto attackers . In October 1687 , the nearby Fort Sainte - Anne and the Senneville mill were attacked by Iroquois , and although several settlers were killed , the attackers were repulsed . A second attack was more successful in 1691 , and the fort was burned down . Only the mill itself was left standing . Second fort . The attack had come shortly after the 1690 Battle of Quebec , and an enraged Governor - General Frontenac ordered the construction of a second , more imposing fort . The fort was rebuilt in 1692 with thick stone walls and corner tower bastion s . With extensive cannons and swivel wall guns , it was the " most substantial castle - like fort " near Montreal . It was never attacked again . The windmill was rebuilt in 1700 , and was probably still in use until the 1780s . In 1703 , Jacques Le Ber de Senneville constructed a large stone house and fort in order to improve and protect his fur trading operations , and the local seigneural manor house was built in 1706 . However , after the fall of New France in 1763 , it was not used by the British as a military post . In 1776 , Fort Senneville was destroyed during the American Revolutionary War by Continental Army troops under Benedict Arnold , in military maneouvres associated with the Battle of the Cedars . In 1865 , the property was purchased as a summer residence by John Joseph Caldwell Abbott , former prime minister of Canada and Mayor of Montreal . Sir Edward Seabourne Clouston purchased the domain from Abbott ' s estate in 1898 . The site today . The site remains private property . The area today is important part to Montreal ' s cultural and natural heritage for several reasons . In November 2003 , Quebec recognized its historical significance by classifying it a " " Site historique " " . The Ministry of Culture and Communications has commissioned studies on the historical ownership of the fort , and funded archaeological research and repairs to consolidate the structure of the ruin , recognising " the exceptional historic and prehistoric archaeological potential of the ruin and its surroundings " . The site ' s value today includes its ecological and environmental significance , and its shoreline , which is in a semi - natural state , is part of the habitat for the rare map turtle . It is situated between the Lake of Two Mountains and the Senneville Forest ecoterritory , as described in Montreal ' s Natural Spaces Policy . Therefore , it could be considered part of the wildlife corridor ( " lien faunique " ) between the lake and the forest .