The Serenissima's vegetable plot
North of the Lido, Sant' Erasmo was originally a port for Murano but soon found its role as an island of forts and gardens. Of the fortifications, the most notable is the enormous, recently restored Torre Massimiliana, begun by Napoleon and completed by the Austrian Archduke Maximilian in 1843-1844 (and it came in handy, as he later had to take refuge there). It was used by the Italian army until the First World War; in 1943 the Germans added an anti-aircraft battery. Now it's been beautifully restored as a museum and exhibition space.
Elsewhere, flat, peaceful, sparsely populated Sant' Erasmo, criss-crossed by rustic lanes, is the 'Venetian countryside' a timeless place where patricians once came in the summer and where Venetians, suffering from mal de pierre and the tourist hordes, come to get away from it all. In spring, the purple artichokes (carciofo violetto di Sant'Erasmo) are famous, and amidst the vegetable plots, you'll find orchards and vineyards, canals and forgotten hunting lodges. Wading birds populate the shores (with its mudddy shallows, the island is an important resting spot for migratory species). Fishermen in summer catch clams for spaghetti alle vongole, and people come to swim by the laid-back café just under the Torre Massimiliana.
The Cooperative Lato Azzurro B&B, a ten-minute walk from the Caponne vaporetto landing (041 5230642) hires out bikes for exploring. If you prefer to walk, try disembarking at the Chiesa stop and walking towards Capanonne. Always check the vaporetto schedules so you don't get stuck overnight. And bring binoculars.