The most recent part of the delta, which projects into the Adriatic between Chioggia and Comacchio, contains channels that actually connect to the Adriatic and on that account is called the active delta by the park authorities, as opposed to the fossil delta, which contains channels that no longer connect the Po to the Adriatic (but once did). The active delta was created in 1604 when the city of Venice diverted the main stream, the Po grande or Po di Venezia, from its channel north of Porto Viro to the south of Porto Viro in a channel then called the Taglio di Porto Viro, "Porto Viro cut-off". Their intent was to stop the gradual migration of the Po toward the lagoon of Venice, which would have filled up with sediment had contact been made.