Ometepe is two volcanoes standing in Lake Cocibolca, Nicaragua's great lake, welded into a single figure-eight island by their own lava. They grew separately until their skirts met at a low isthmus, and they remain two different places. The crossing from San Jorge takes an hour. Concepción starts as a triangle on the horizon and ends up towering over the boat while you stand at the rail with islanders and their sacks of produce. It is the live one. The climb leaves the plantain farms, goes up through forest and breaks out onto an open slope of loose black ash where every step slides back half of itself. Eight to ten hours with no shade, and cloud sits on the summit most days, so you can climb all of it and see nothing. On a clear one both lobes of the figure-eight stand clear.
Maderas is the dormant twin and the dirtier hike: a knee-deep mud staircase through cloud forest dripping with moss and bromeliads, howler monkeys overhead. At the top the ground drops away into a crater holding a flat green lake, usually half-swallowed by fog. Between them the island is farm country, and a rented bicycle on the dirt roads is how it is actually seen: banana rows, coffee plots and pasture, potholes, river crossings, and a cone always over your shoulder. Rain that fell on Maderas filters down through the volcano and comes back up at Ojo de Agua, cold and glass-clear under the trees. Down on the shore, Cocibolca is fresh water, but the wind drives real surf onto dark volcanic boulders and the far side drops below the horizon: waves, spray and no salt. Bull sharks live in it too, and they were never sealed in by geology: they come up the river from the sea and go back down. And on Maderas's lower slopes, the boulders are covered in carving — spirals, faces and figures cut over centuries, the oldest about 2,300 years old. They sit out in the coffee and the pasture with no glass between you and them.