The Quabbin Reservoir is the largest inland body of water in Massachusetts. Despite being located aprox. 100 km from Boston, it is Boston's primary water supply. Quabbin was built between 1930 and 1939, then slowly filled, when in 1946 it reached its current size.
To create the reservoir, four towns were flooded. There are nice trails around Quabbin, some even paved, named "Old main road", which leads staight inside the water...
As Quabbin is drinking water reservoir, swimming is prohibited there. There are nice hikes all around the reservoir, roads leading to gates where driving is not allowed but pedestrians are welcomed. Nice walks, many of them leading to wonderful beaches: take your picnic basket and enjoy the view, or rent a boat at Winsor dam and enjoy a trip (fishing is allowed as well).