Get a dose of vitamin D at Cala Cortina. After you've worked on your tan, hang around and watch the sky turn kaleidoscopic as the sun starts to set.
Situated in Santa Lucía, this stretch of coastline is worth a look. But you'll find lots more to see and do in the area. Roman Theater, Punic wall of Cartagena, and Morena Beach aren't too far away from Cala Cortina.