Montreal is usually given three days and usually deserves four. Not because it holds more than a comparable city, but because its good parts are stacked in bands rather than gathered around a centre. Move between bands carelessly and you lose an afternoon. Move between them once a day and you lose almost nothing.
Picture three strips laid against the river, with a wooded hill dropped into the middle of them. The lowest strip is the old town and the port, running east to west along the St Lawrence. Above it sits the downtown grid, backed up against the mountain. North of the mountain runs the long residential spine, the Plateau into Mile End into Little Italy, threaded along a handful of north-south streets you can walk end to end. Then, hooking west out of downtown along a disused industrial waterway, there is a fourth strip: Little Burgundy, Saint-Henri, Verdun.
Three days means abandoning one of those four. Four days gives each one a morning and an evening, which is roughly how residents use them.
The second thing to settle before you book is which day of the week you arrive. Montreal's museums largely close on Mondays. The Musee des beaux-arts and Pointe-a-Calliere both do, and they are the two you would otherwise build a day around. Several of the older lunch counters shut then too. A Monday is not a lost day, but it has to be spent outdoors, and knowing that in advance is worth more than any other single piece of planning here.
Day one: the river strip, and one thing booked from home
Start low. Old Montreal is small, cobbled and at its least oppressive before mid-morning, so walk Saint-Paul and Place Jacques-Cartier early and get the photographs out of the way while the tour groups are still at breakfast.
Two things down here are worth real time. Notre-Dame Basilica is the obvious one, and the calculation most visitors get wrong is the evening rather than the daytime visit: the AURA projection show staged inside the church runs about half an hour, costs in the region of CAD 30 at the time of writing, and sells out regularly through the summer. Book it before you leave home rather than hoping. The less obvious one is Pointe-a-Calliere, built directly over the ground where the city was founded, which takes you underground through the original foundations and along a stretch of nineteenth-century collector sewer. Give it two hours. It typically opens mid-morning and closes in the late afternoon, and weekend openings usually start an hour later than weekdays, so check the day you plan to go.
Break for lunch in the old town, where Olive et Gourmando is the long-standing sandwich and pastry answer, then walk east along the water into the Old Port. If you want the afternoon to stop moving, Bota Bota is moored there: a Nordic spa built into a converted ferry, which opened a second and much larger floating pavilion alongside the original vessel in 2026. Expect a water-circuit pass to absorb a meaningful share of a day's budget, and book a time slot rather than turning up.
Finish with a drink somewhere other than the old town, which prices its bars for hotel guests. Bar Le Mal Necessaire, the tiki bar that moved out of Chinatown proper into the International Quarter a few streets north, is ten minutes on foot and a different city.