dark, colorful textures of the walls in a lava tube of canaria island

dark colorful textures walls lava tube canaria island travel tunnel cave underground rock volcano volcanic geology inside park lighted light portugal portuguese porto judeu roofs textured speleology stone touristic wall background geothermal magma nature scenic terceira illuminated angra do heroismo europe coal azores aores destination deep interior black caving carvao basaltic crack attraction algar caldeira guilherme moniz cavern colorfultextures