At this point , Rio Aconcagua cascades through a narrow gorge worn in the course of ages through the solid rocks. The near perpendicular walls are about 60 m high and the railway passes through a series of three short tunnels finally to emerge some 6 km further up the valley, and about 100 m higher, at Rio Blanco, 1420 m above sea level.

Salto del Soldado is so called because it's said that, during the struggles for independence, a Chilean soldier being pursued by the Spanish army, escaped persecution by leaping on his horse across the chasm. I guess the chasm is about 9 m wide at the top so it's just about possible. Mind you, the landing must have been pretty perilous.

There's a more spectacular view of the waterfall in this shot. At one time, trains on the Transandine Railway (Ferrocarril Trasandino) passed through the tunnel. You get a better view of the line from this shot. Both those photos are on the Turismo Ciudad Andes website. And there's an old photo of a train entering the tunnel from the other side here. It's from the website of El Ferrocarril Trasandino: Fotos históricas. There's also a c1905 photo of the waterfall here.