Formed about 4,000 years ago when the Montana La Corona volcano erupted, Cuevas de Los Verdes is one of the longest volcanic tunnels in the world and is visited by thousands of people every year. These astonishing caves are also known as the ”Green Caves' and are located in a protected area within the Monumento Natural del Malpais de La Corona. Take a guided tour of the caves to learn about their history, including the days when local people used to hide in them from pirates. Look out for the wonderful range of colours on the walls of the caves, especially reds, which come from the oxidation of iron. You'll also be shown their mind-bending optical illusions. It's about six miles from the crater to the sea and there are over 15 Jameos or openings that allow you access to different caves deep underground. Tours only cover a kilometre so it's not tiring and all ages can enjoy the caves. During summer, it's best to visit in the afternoon if you prefer to avoid crowds. It's definitely something you should make time to visit whilst on your holiday in Lanzarote as it's one of the most attractive volcanic structures on the island.