It is the oldest and biggest of the forts of the "Campo Trincerato" of Mestre. It's construction was started by the Austrians during the first part of the 19th century and was finish by the French. It represents the first example of a fortified construction for the defence of Venice and for the defence of the arsenale from attacks by the mainland.
Occuping an area of about thirty hectares it is today temporarily owned by the Community of Venice who use it to hold conferences and events in the summer. 

Forte Marghera is open from Tuesday to Sunday, for details check the official website