Fodor's Expert Review Gruta do Lago Azul

The 160-foot-deep Gruta do Lago Azul has a crystal clear freshwater lake at the bottom and smaller side caves in the calcareous rock. The best time to visit is from mid-November to mid-January at around 8:30 am, when sunlight beams down the entrance, reflecting off the water to create an eerie turquoise glow. See stalagmites and stalactites in various stages of development.