Despite being right next to the main Lisbon - Cascais road, the "Marginal", Praia das Avencas is somewhat tucked away under the steep cliffs which overlook this beach. For this reason, unless you are actually looking for the beach you are unlikely to notice it.
Praia das Avencas is a fairly small beach with the cliffs providing good shelter from the wind. Above the tide line the beach is completely sandy but as the tide drops out the sea bed becomes increasingly rocky. This is great news for snorkelling and the beach has been classified a "Zone of Biophysical Interest" as a result of its ecological importance. In addition, you can rest assured that the water is clean as the beach is a Blue Flag award winner.
The beach here is relatively exposed to the Atlantic swells and there can be quite powerful waves. Fortunately the beach is patrolled by lifeguards during the summer months making bathing safe. At the foot of the cliffs is a beach bar / restaurant serving everything from snacks to full meals.
Like all the beaches along the Lisbon - Cascais "Linha" Praia das Avencas is easily reached from by train with Parede station only a short walk away.
Praia das Avencas owes its name to a plant - the Avenca - which grows here. This plant has a long tradition of medicinal use in Portugal.