Panorama of Campo San Zanipolo with the Basilica Santi Giovanni e Paolo on the right Source: https://commons.wikimedia.org/wiki/File:Veneto_Venezia4_tango7174.jpg Author: Tango7174
Sestiere Castello is one of the six sestieri or neighborhoods of Venice. It is the largest as well as westernmost neighborhood of the city. It borders Sestiere Cannaregio to the northwest and Sestiere San Marco to west, and is surrounded by the Venetian Lagoon on the north, south and east.
Sestiere Castello comprises a number of islands including San Pietro di Castello, Isole Gemini, and Isola di Sant'Elena. It was named after the islands of San Pietro di Castello, which has been inhabited since the 8th century.
Arsenale at Sestiere Castello Source: https://commons.wikimedia.org/wiki/File:38VeneziaArsenale.jpg Author: MarkusMark
The main feature of Sestiere Castello is the naval dockyard, which developed on Isole Gemini. It is still functioning today, and is part of Arsenale, a complex of shipyards and armories that was once the largest in Europe.
Isola di Sant'Elena was originally separated from the rest of Sestiere Castello, but recent land reclamation has neared the distance to just a gap connected by three bridges.
The Rio de Palazzo separates Sestiere Castello from Sestiere San Marco. The New Prison was located on the Sestiere Castello, and prisoners were taken across the Bridge of Sighs to their trial at the Doge's Palace.
The Bridge of Sighs across the Rio di Palazzo between Sestiere Castello and the Dode's Palace in Sestiere San Marco Source: https://commons.wikimedia.org/wiki/File:Venice,_Bridge_of_Sighs.jpg Author: ChristianBier