Along the coast between Setúbal and Sesimbra, the Serra da Arrabida stretches up. These chalky hills have the only surviving example of primitive Mediterranean vegetation. Tucked away in the heart of Arrábida's Natural Park, the formation goes back 180 million years. The soil and mild climatic features, considered the best in Portugal, have produced a lush vegetation rich in species.
The Arrábida Natural Park was formed in 1976 and covers an area of 10,800 hectares. Setúbal, Palmela, Azeitão, Sesimbra and the sea make up its boundaries. The countryside is hilly and we can find the Serra dos Gaiteiros, S. Luís, S. Francisco, Louro, Risco along with the highest hills, the Serra da Arrábida which stands at 499 metres high. This ends abruptly and cuts into the sea, providing a scene of picturesque beauty with the lush green vegetation and the chalk white face of the cliffs, such beauty which inspired poets like Sebastião da Gama.
On the coast, between the sandy beaches and clear water, up above, breeding grounds for birds of prey abound and one can also find a typical maritime flora which extends as far as the Serra do Risco, the highest coastal point of continental Portugal (300 metres above sea-level). In Creiro, around the Pedra da Anicha, an island traced above the sea leads us to the only zoological reserve of the Natural Park, named so because of the value of underwater plant species found there
Part or or all of this text stems from the original article at: http://www.portugalvirtual.pt/_tourism/costadelisboa/costazul/naturezu.html