GRUTA DO NATAL

Named literally "Christmas grotto" after the mass celebrated there on December 25, 1969, gruta do Natal is just 6 km from Algar do Carvão. It's a 697-metre-long lava tube. You won't be able to go all the way down, as part of it is reserved for experienced cavers, but the two routes inside will enable you to observe all kinds of volcanic formations. A helmet is provided, as some passages are narrow and require you to bend down to move forward. A great underground expedition!