By No machine-readable author provided. Thierry Caro assumed (based on copyright claims). – No machine-readable source provided. Own work assumed (based on copyright claims)., Public Domain, Link
The Trou de Fer (“Iron Hole”) is a canyon on Reunion Island, off the coast of Madagascar in the Indian Ocean. The primary river flowing through the gorge is the Bras de Caverne River, a tributary of the Rivière du Mât. The canyon has two distinct parts: a large crater, which is fed by six prominent waterfalls, and a narrow slot canyon at its outlet, which constitutes most of the canyon’s length. The slot canyon, or “The Corridor”, extends for about 3 km (1.9 mi), and is said to be commonly dammed up by debris jams to form lakes, including the “Lake of the Eel”. Many springs flow through the porous volcanic rock of the walls, creating countless waterfalls.
By Mart.wain [CC BY-SA 4.0 ], from Wikimedia Commons
User: Bbb at wikivoyage shared [GFDL or CC BY-SA 3.0 ], from Wikimedia Commons
By Samuel Busson [CC BY-SA 3.0 ], from Wikimedia Commons
By Jennifer_greatoutdoors (Flickr) [Public domain], via Wikimedia Commons
e MORFES 
Beautiful reminders that there are still some places that belong exclusively to the natural world and are beyond the reach of man.
Bewildering pics
La natura non finisce mai di stupirci con le sue grandiose immagini
Buona domenica e un saluto,silvia
Incredible.
It can not be denied that the photographs are of the highest quality.