of Portugal — the Costa Verde. It is bordered to the north by the municipality of Esposende, to the northeast by Barcelos, to the east by Vila Nova de Famalicão, and to the south by Vila do Conde. To the west, it has a shoreline on the Atlantic Ocean. The rocky cliffs, common features downstream of the Minho's estuary, disappear in Póvoa de Varzim, giving way to a coastal plain. The plain is located in a cuspate foreland, an old marine plateau from the Plio-Pleistocene, conferring a sandy soil to the coastal lands. The sand dunes in the Northwestern coast formed during the Little Ice Age and started piling up in the 15th or 16th century. Wandering along the coast one discerns Cape Santo André, the tip of the cuspate foreland and the Avarus Promontory, referred to by Ptolemy. São Félix Hill () and Cividade Hill () rise above the landscape. Despite their modest rise, the expanse of the plain makes them easy reference points on the horizon. The mountain chain known as Serra de Rates divides the municipality into two distinctive areas: the coastal plain and hills where the forests become more abundant and the soils have less sea influence. In this landscape dominated by the plains and low hills, only the hillside of Corga da Soalheira () in the interior, is dissimilar. There are no large rivers, but abundant small water streams exist. Some of these streams are permanent, such as the Este River, which feeds into the Ave. The source of the Esteiro Stream is located at the base of Cividade Hill and empties at the beach of Aver-o-Mar, while the Alto River's source is at the base of São Félix and reaches the Atlantic at Rio Alto Beach. The land is well-irrigated, springs and wells are very common since underground water is often close to the surface. The forest areas suffer from strong demographic pressure and intensive agriculture. Some forests locally known as bouças are defined areas with maritime pines, oaks and eucalyptus plantations. Forests are still important in parishes surrounded by the Serra de Rates, whose flora is distinguished by the pedunculate oak or the european holly. In the 18th century, the monks of Tibães planted pines, which characterized the civil parish of Estela. In the past the Atlantic forest predominated, with trees such as oaks, ash trees, hazels, strawberry trees, holm oak, and alders.