The water going over Saltos del Monday is rust-red and the rock under it is black, and they are the same material at two ages. The falls are on the Monday river in eastern Paraguay, ten kilometres from the Brazilian border: three main curtains and a scatter of smaller ones, about forty metres down and 120 across. The black is basalt, old lava from the same sheets that step Iguazú. Weathered in a hot, wet climate, the iron in it rusts and the rock rots down into the deep red clay of Alto Paraná. That clay is what the rain now strips off the cleared fields and carries into the river. The lip is not a clean edge either. Basalt outcrops cut it into separate falls, each island carrying its own crown of trees, which shows you the ledge underneath.
A glass lift drops forty metres from the rim to the bank, and the falls grow as you sink past them. At the bottom the walkways carry you toward the water until the roar is something you feel in your ribs, and the spray settles on your skin. A steel cable runs 275 metres over the gorge, ridden at about thirty kilometres an hour, ending a few dozen metres short of the water with the full width of the falls under your boots. Behind the falls the shaded trails run through one of the last standing fragments of the Alto Paraná Atlantic Forest, which has almost disappeared from Paraguay. The name has nothing to do with the English weekday: it is Guaraní, said closer to mon-da-ú, and usually read as the water that steals. This is the wettest corner of the country, with no real dry season, so the falls never stop. Summer storms thicken the three curtains toward one wall and the spray blots out the lower decks; the July low separates them cleanly again. The falling curtain is a wall nothing that hunts will cross. Great dusky swifts pour into the gorge at dusk and settle on the soaking rock right beside the water.