Poço Azul (Blue Pool) is a subterranean pool of startling clarity in a limestone cave in the municipality of Novo Horizonte, on the eastern edge of the Chapada Diamantina region. The pool is lit from above by a shaft of natural light that, at midday, turns the water an extraordinary electric blue — a colour that seems too vivid to be natural and has made Poço Azul one of the most photographed spots in all of Bahia.
Swimming in the pool is permitted (it is one of the few caves in the park where this is allowed) and the experience of floating in the blue-lit water, surrounded by the cave walls, is exceptional. The pool is spring-fed and cool even in the hottest months. Tours from Lençóis typically combine Poço Azul with nearby Poço Encantado (the other famous blue cave in the region, where swimming is not permitted but the blue light effect is even more intense). Both require a drive of about 1.5-2 hours from Lençóis plus a guide.