Aymeric. Tourists exploring the area lavatubes Grand Brûlé. Ancient Caves Although there are a number of other ancient lava tubes in Reunion including The Bateau Caverne we have chosen to highlight three ancient lava tubes have been extensively documented by Pascal Colas. Grotte de la Grand Ravine in Trois Bassin Grotte des Tamarins in Saint Paul Grotte du Bassin Bleu in L'Eperon Grotte de la Grand Ravine. By far the most impressive lava tube on the island its two inputs are approximately 80m along a route of 200 meters over the Grand Canyon ravine. This cave was first explored for the exploitation of guano produced by swiftlets in the 19th century, but its 473 meters is not widely explored until 2004 by Pascal Colas. The northern and southern segments joined in 2005 with a wide excavation. Excellent topological studies and reports of progression of exploration are available at the website Pascal Colas', and there are some photos provided by WinsterCavers.