The first point of contact between the Porto Conte Regional Nature Reserve and the city of Alghero is the Calich wetland, which can be reached along Viale Burruni (a road branching off Via Don Minzoni), or alternatively by coming through Fertilia from Porto Conte and then entering the city of Alghero.

The Calich lagoon extends across around 92 hectares and has an average depth of around 1.5 metres. The banks are generally low-lying and sandy, whereas the bed is muddy. This elongated lagoon, which stretches out in a north-westerly/south-easterly direction, runs parallel to the coast along the highway that leads from Alghero to Fertilia. Its origins are associated with the damming – due to the accumulation of detritus – of two major tributaries: the Rio Barca and the Rio Calvia. A sandbar, in the form of the current Maria Pia beach, separates it from the sea, with which it is linked through a single channel that is used as a marina for tourist vessels and fishing vessels.

The lagoon is recognised as a wetland of international importance for its natural environment, but it also has a significant role to play in economic terms, since it is used both for professional fishing and for tourist and recreational activities, such as birdwatching – an activity that is facilitated by the observation points installed by the park authority. Over recent years, the wetland has been regenerated to improve accessibility, specifically along the shore that runs parallel to Viale Burruni. Visitors can experience all that the lagoon has to offer by making their way to the birdwatching station located on Viale Burruni or by taking the path or cycle route towards the Romanesque bridge.