Cabo de São Vicente is the very south-western tip of Portugal (and Europe), and the cliff of the Promontorium Sacrum, as the Romans called it, was the last land the Portuguese Navigators saw before setting course for the open Atlantic in the 15th century - an amazing leap of faith which they may well have expected to be a one-way journey.
The cape takes its name from Saint Vincent of Saragossa, patron saint of both sailors and of Lisbon. Legend has it that the martyred saint's body was buried on the cape, and his grave was guarded by ravens. His remains were later relocated to Lisbon, again accompanied by ravens. This scene is depicted on Lisbon's coat of arms. (Of course there are other, parallel stories. He is also venerated in Valencia, for instance.)
St. Vincent's memorial day, by the way, is next week: 22 January.