One of my favorite bike paths in Montreal is alongside the Lachine canal. While the stretch between the Old Port and Atwater Market is nicely developed and great for hanging out with all of its green spaces, further west things become particularly nice. The city skyline starts to retreat further, the trees become denser, and the green spaces wider. The feeling that I am no longer in the city becomes stronger, regardless of being only a few kilometres further along the path. (The Lachine canal ends in Lachine, at the St Lawrence River.)
Only 12km from the Old Port, the bike path reaches the beautiful waterfront Park René-Lévesque. A sculpture garden, picnic tables, and plenty of space in front of the water are available. My favorite thing to do is bike all the way to the end, from which on a windy day the waves crash against the rocks and it really feels like I am very far from downtown Montreal.
I like to bring a book and some snacks, and sit close to the water, resting until I am ready to bike the 12km back to the city.