Alto Toroni, Volcano on the Bolivia–Chile border, Tarapacá Region

Alto Toroni, also called Sillajhuay, is a heavily eroded volcano on the Bolivia–Chile border whose summit reaches about 5,995 metres. Only a small eastern sector lies in Bolivia. Above 4,100 metres glaciation has removed any recognizable crater, while lower slopes preserve 30–90-metre-thick lava flows and deep valleys such as Río Blanco.

Alto Toroni, also called Sillajhuay, is a volcano on the Bolivia-Chile border built on older ignimbrites. It was active within the last million years but not in recent times, as heavy glacial erosion above 4,100 m has left no recognizable craters. Non-eruptive activity continues as surface deformation and earthquakes.

The name Sillajhuay comes from Aymara and is usually translated as "devil's chair"; silla may instead derive from sila, meaning llama. The mountain stands on the Bolivia-Chile border, with only a small eastern sector in Bolivia, and the nearest villages are Cancosa and Villa Blanca, 16 and 18 km away.

Climbing requires good physical fitness and several days for acclimatization to the altitude, as the terrain is very exposed. The best time to ascend is during drier months when conditions are more stable.

Sillajhuay's summit region is poorly accessible and above 4,100 m glaciation has eroded it so heavily that no recognizable crater remains. Its ice is firn, including penitentes, above 5,750 m; between 1989 and 2011 this firn lost over half its surface.