Of the three lagoons, it is the lowest. Like the other two, it forms part of a particularly sensitive nature reserve and access to it is prohibited, but, in addition, given its greater inaccessibility due to its greater distance from the edge of the private estate on which it is located, it is the safest and most isolated refuge for birds. It can be seen in its entirety from some points along the Roman road.
The Small Lagoon, which covers an area of around 12 hectares, is between one and a half and two metres deep, although up until half a century ago it could have been more than twice as deep. However, the material dissolved in the runoff water that flows into the lagoon has gradually clogged it over time. It is precisely this circumstance and its rectangular geometry that has prompted an interesting line of study on its origin as a clay extraction pit for the manufacture of ceramic amphorae.
Its vegetation consists mainly of reeds, chestnuts, bayuncos and rushes, perimetered by a continuous line of tamarisk, which makes it a particularly suitable refuge for small and medium-sized birds.
Among the species that live in these lagoons are flamingoes, ruddy ducks, horned coots, marbled ducks, red-crested pochards, stilts, mallards, lapwings and the glossy ibis.