Cirque du Fer-à-Cheval

The Cirque du Fer-à-Cheval is a natural glacial cirque located in the commune of Sixt-Fer-à-Cheval, in the Giffre valley, at the heart of the Sixt-Passy National Nature Reserve. It forms a limestone horseshoe spanning 4 to 5 kilometres with vertical walls 500 to 700 metres high, crowned by peaks approaching 3,000 metres altitude (Pic de Tenneverge 2,989 m, Cheval Blanc 2,831 m, Grenier de Commune 2,775 m). It is the largest mountain cirque in the Alps.

Its name comes from the horseshoe shape of its cliffs, which close off the eastern part of the Giffre valley. In spring, over thirty waterfalls fed by snowmelt cascade down its walls to form short streams, tributaries of the Giffre. The most famous are the Pleureuse, Sauffaz, Méridienne, Fontaine de l'Or (Pierrette), and the Lyre. Classified as a Grand Site of France, the cirque welcomes approximately 500,000 visitors annually and forms part of Haute-Savoie's largest nature reserve (9,200 hectares of 11,200).

The cirque's rocks are Jurassic limestone, heavily fractured. High rainfall intensifies erosion: a major rockfall occurred in 1602 (burying several hamlets, commemorated by a chapel), then in 2003 (300,000 m³) and September 2025 (35,000 m³ at Pas Noir), leading to temporary closure of the Fond de la Combe sector by municipal order.