The Tróia peninsula is actually a gigantic sand dune, which was gradually formed over thousands of years.
At the edge, where the waves break, the first colonising plants such as the European searocket can be found. Then, on the embryonic dune, we find the Elymus farctus and the Otanthus maritimus. Next come the primary dunes, with tall ridges and only a few years of life, covered in Ammophila arenaria. Over the ridges there are the secondary dunes, several decades old, rich in aromatic shrubs. The further inland we go, the older the dunes are, sustaining larger bushes, such as the Lygos monosperma and the Juniperus communis, and even the stone pine.
In winter, flocks of small birds – sanderlings – swarm the shore and in spring, they migrate north, to the North Pole, to nest.