The Algar do Carvão is a stunning underground cave located on the island of Terceira in the Azores archipelago. It is known for its unique geological formations, including stalactites, stalagmites, and lava flows, which have been formed over thousands of years.

Visitors to the Algar do Carvão begin their journey by descending a spiral staircase into the mouth of the cave, which is located in the middle of a large volcanic cone. As they make their way deeper into the cave, they are treated to breathtaking views of the underground world, including crystal-clear pools of water, eerie caverns, and intricate rock formations.

One of the most striking features of the Algar do Carvão is the large lake at the bottom of the cave, which is fed by an underground river. Visitors can take a boat tour of the lake, which offers a unique perspective on the cave's geological wonders.