Treviso is a walled medieval city about 30 kilometres north of Venice that most visitors pass through on the way to somewhere else. That's their loss. The historic centre has canals, arcaded streets, towers, and a cathedral with frescoes by Titian — all on a much more human scale than Venice, without the crowds or the prices.
The city is also the birthplace of tiramisu (still served at Le Beccherie, where it was reportedly invented in 1972), and the local food scene is quietly excellent. Radicchio di Treviso — the bitter red chicory grown in the surrounding hills — appears on every menu in autumn and winter. The covered Pescheria fish market on a canal island is one of the most atmospheric in the region.
Easy day trip from Venice (30 minutes by train) but comfortable enough as a base for exploring the Prosecco hills to the north.