Pedra de Lume is one of Sal's most unusual sights — an extinct volcanic crater that was breached in the 19th century to let seawater flood in, creating an inland salt lake about two kilometres from the coast. The salt has been harvested here for centuries, and the old industrial infrastructure — rusting tramways, salt pans, and processing sheds — still stands around the lake's edge.
The water in the crater is so dense with salt that floating is effortless, which has become the main tourist draw: visitors strip off and bob around in the intensely saline water, which is said to have therapeutic properties. It's a genuinely strange and enjoyable experience. The salt concentration is comparable to the Dead Sea. Bring flip-flops (the lakebed is encrusted and sharp), sunscreen, and something to rinse off with afterwards — the salt dries out your skin quickly.
Pedra de Lume is about 8 kilometres from the main town of Espargos; take a taxi or join an organised day trip.