Buracona, on the northwest coast of Sal near the village of Santa Maria da Espargos, is a volcanic rock formation where the sea has carved a tunnel through the lava. At the right time of day, sunlight enters the tunnel from below the waterline and illuminates the pool at the far end with a vivid, luminous blue — the "Blue Eye." The effect is striking when conditions cooperate.
The site is part of a longer stretch of dramatic coastline accessible on foot from the road. The area around the tunnel is a protected natural reserve; swimming is not permitted in the tunnel itself, but the surrounding rocks offer reasonable snorkelling in calm conditions.