 The parish seat of São Marco is north-northeast of the centre of Silves and is south-southeast of Lisbon.Located between the junction between the Serra do Caldeirão and the Serra de Monchique mountain ridges, the parish is intersected by the Riberia de Odelouca, which bisects the main village, also known as the Ribeira de São Marcos.The Odelouca receives water from two tributary streams