Praia Da Ursa translates to "Bear beach". It is in our opinion one of the most amazing beaches near Lisbon. The main reason is the long stretch of shallow water and the fact that it's often completely empty. The reason for that is that it is a fair walk down and, well, also back up. For us it isn't too bad walking up and down, but for those who are not easy on foot, we don't recommend it.
You'll take an "off road trail” down from the parking area and at the end you are rewarded with this stunning beach with amazing rock formations and raw beauty.
However during a windy day you should NOT walk down to the beach, as the cliffs are unsteady and can crumble. Therefore please pay attention to the conditions before going.