The Veiga de S. Simão is a wetland located on the left bank of the Lima River estuary that has an approximate area of ​​700 ha. In addition to the agricultural spaces and dispersed forests, which occur in the driest areas and out of reach of marine waters and occupy an area of ​​approximately 200ha, natural meadows, reeds (Phragmites australis) and bulrush (Typha latifolia). Here, the humid soil can host formations of bryophytes of the genus Sphagnum, and the round-leaved sundew (Drosera rotundifolia) can appear punctually.

Veiga de S. Simão is one of the most ecologically relevant wetlands in the municipality of Viana do Castelo. The relatively complex system of reeds, salty marshes and reed beds, as well as the space corresponding to the lagoons of Vila Franca, deserve special mention and pertinent conservation measures.

These wetlands serve as a refuge/feeding place for several shorebirds and waterfowl.