Murano Island
The vaporetto ferries to the northern lagoon islands leave from Fondamenta Nuove area in Venice (Line LN - Lagoon North), towards the north side (top) of the Castello district (sestiere of Castello).
You can easily walk from San Marco to Fontamente Nove or take the vaporetto lines 41/42 or 51/52. The trip to Murano takes less than 45 minutes and you could spend 3-4 hours to see the biggest island of the venetian lagoon. There are two main vaporetto stops in Murano, the first is “Faro” and mostly suggested “Colonna”, both an easy walk to the main island.
Murano is famous for its glass and there are still some authentic old glass factories. You can go shopping for some glass item or just visit the Museo de Vetro (the Glass museum) and explore the old and new glass collections. Just be careful since there are a lot of shops selling glass products made in China, goods of low quality at high prices.
You can also visit the church of San Pietro Martire and admire the oil paintings of Veronese, Tintoretto and Giovanni Bellini. Last you can visit a very old church, Santa Maria e Donato.