Brockville is a small St. Lawrence River city between Kingston and Ottawa, close to the eastern end of the Thousand Islands. It calls itself Ontario's first incorporated town, and the claim fits the streetscape: old stone and brick buildings, a working waterfront, and a downtown that still faces the river rather than a highway.
The standout is the Brockville Railway Tunnel, Canada's first railway tunnel, now reopened as a walk-through attraction with light and sound installations. It gives the city a memorable hook that most river towns lack.
Brockville is also a useful base for a low-key Thousand Islands day. The Aquatarium explains the ecology and shipping culture of the river, Fulford Place shows off Edwardian wealth, and the waterfront parks make a good pause on the drive between Ontario's bigger cities. It is not a place to cross the country for, but if you are already nearby, Brockville clears the one-day test easily.