With more than 300 species of birds, Puerto Vallarta is called El Paraiso or Paradise. The most compelling feature of the area is the huge bay, the Bahia de Banderas or Bay of Flags, cut like a semicircle out of the Pacific Coast of Mexico. The coastline of the bay is relatively featureless, except for a few small inlets at the mouths of rivers, such as a Yelapa, Boca de Tomatlan, and Mismaloya. In the mouth of the bay is a small cluster of rocky islands, the Marietas or Islas Marietas where some sea birds nest in season.