Poço Encantado (Enchanted Pool) is a subterranean lake in a limestone cave near Itaetê, about 2 hours from Lençóis. Between April and September, when the sun angle is right, a beam of natural light enters the cave through a skylight and illuminates the water from below, creating a vivid aquamarine glow that fills the entire cave chamber. The effect lasts for about two hours around midday and is one of the most spectacular natural light phenomena in Brazil.
Swimming is not permitted in Poço Encantado (the cave is legally protected as a pristine ecosystem), but visitors walk down to a viewing platform at the water's edge. The visual effect at its peak — the water appearing to glow from within, the cave walls reflecting the blue light, the narrow shaft of sunlight cutting through the darkness above — is sufficiently extraordinary that the no-swimming rule is easily forgiven. Tours combining Poço Encantado with nearby Poço Azul (where swimming is permitted) are the standard approach.