Trou aux Cerfs is a dormant volcanic crater that last erupted around 700,000 years ago and is now so thoroughly overgrown with rainforest that from the rim it appears as a dense green bowl rather than a geological feature. The crater is 85 metres deep and roughly 200 metres across. A paved road and jogging track run around the perimeter, and on clear days — more likely in the dry season between May and November — the views from the rim extend across most of Mauritius.
The site is free to enter and open at all hours. Early morning is the most atmospheric time, when mist fills the interior and the surrounding plateau is cool and quiet. The walk around the crater rim takes about 20 minutes at a stroll. Benches are placed at intervals. It's a short walk or inexpensive taxi ride from the centre of Curepipe.