From the thirteenth century onward, the district grew around a naval dockyard on what was originally the Isole Gemini. The land in the district was dominated by the Arsenale of the Republic of Venice, then the largest naval complex in Europe.
Other significant structures were by the monasteries in the north of the quarter.
Prominent sites and buildings in Castello include:
- Church of Santi Giovanni e Paolo (San Zanipoli)
- Church of San Giorgio dei Greci
- Campo Santa Maria Formosa and Church of Santa Maria Formosa
- Church and Ospedale della Pietà
- Church of San Zaccaria
- Scuola of San Giorgio degli Schiavoni
- Scuola di San Marco
- Venetian Arsenal
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