As part of a clever advertising campaign for European insurance companies Europ Assistance IT and Genertel, ad agency M&C Saatchi Milano installed a full-size submarine in the ground in the center of Milan. There was even a live performance to go along with it to help convince bystanders that a submarine had actually crashed through the street, complete with emergency personnel, and a submarine crew.
http://www.youtube.com/watch?v=Vep7kL1EC0w