One of the natural values that the municipality of Óbidos boasts is the Óbidos Lagoon this is the coastal lagoon system to a greater extent in Portugal, a system extends upstream for two channels, to the west by the Bom Sucesso Arm and for this, the Barrosa’s arm. This lagoon is the land border to the north with the county of Caldas da Rainha, particularly in the parishes of Foz do Arelho and Nadadouro, and the south with the municipality of Obidos, in the parishes of Vau and Santa Maria. Regarding the fauna found in Obidos Lagoon, consists of fish species such as sea bass, sole, plaice, turbot, golden, the sea bream, mullet, even species such as clams, cockles, mussels, the shrimp, octopus, eel, green crab, among others. With regard to the avifauna community, this is an important ecological role in the ecosystem, identified species such as the heron, mallard, oystercatchers, long, curlew leg, tern, heron boieira, snowy egret, gaivinha black beak.