These are the Cuevas de Mármol, or Marble Caves, found on the shores of Lake General Carrera - a remote glacial lake surrounded by the Andes mountain range and spanning the Chile-Argentina border. Formed over 6,200 years as countless waves crashed against a huge peninsula of calcium carbonate, that distinct, swirling pattern reflects the lake's bright blue colours, which can change in intensity and hue depending on the time of year.
