The lagoon is part of Venice. Give it at least half a day: start early, and go by water bus.
Murano
The glass island, with its furnaces and the Glass Museum. It is the closest: water bus lines 3, 4.1 and 4.2. The “free” boat trips to a glass factory offered around St Mark’s usually end with a sales pitch; you are better off going on your own and choosing a furnace demonstration.
Burano
Fishermen’s houses in bright colours, lace, and fish risotto. Line 12 from Fondamente Nove takes about 40 minutes.
Torcello
Where the history of the lagoon began. Today there are a few houses, fields and the Basilica of Santa Maria Assunta, with Byzantine mosaics and a huge Last Judgement. It is a few minutes from Burano by water bus, and very quiet.
Lido
The long island between the lagoon and the sea: beaches in summer, Art Nouveau villas, and the Film Festival at the end of August. Line 1 from San Tomà goes all the way there.
San Giorgio Maggiore and the Giudecca
Opposite St Mark’s, Palladio’s San Giorgio Maggiore has one of the best views of Venice from its bell tower. Next to it, the Giudecca is a residential island with Palladio’s Redentore and a long waterfront looking back at the city. Line 2 stops at both.