Seen from the air, Ometepe Island looks like an hourglass as a slim isthmus connects the crater of dormant Maderas Volcano to the very much still active cone of Concepción Volcano. It was these volcanoes that inspired Ometepe's name, which is a local Nahuatl word that means "island of two hills."

Though a new airport is scheduled to open on Ometepe this year, most visitors still arrive by ferry across Lake Nicaragua. Also known as Lake Cocibolca, this 3,000-square-mile lake is the largest in Central America and was once filled with bull sharks that adapted to the freshwater conditions and became infamous man eaters. They ruled the lake until fishermen nearly wiped out the population for their fins. Hardy descendants still patrol around Ometepe.

The sight of the island's volcanic craters from the wind-swept waters of Lake Nicaragua inspired Mark Twain to write "they look so isolated from the world, so tranquil, so dreamy" as he traveled through the country in 1866. It's an observation that held true as I journeyed across Lake Nicaragua in 2012. Though Twain never laid foot on Ometepe, I did.

Surviving the island

In 2010, the same year the entire island was named a Biosphere Reserve by UNESCO, the producers of "Survivor" chose Ometepe as the location for the show's "Redemption Island" season. Contestants faced a number of challenges but none of them were as daunting as the No. 1 adventure on Ometepe island: hiking up 5,100-foot Concepción Volcano.

Concepción, one of the most active volcanoes in Nicaragua, has erupted more than 25 times in the past 130 years and puts out a nearly constant stream of ash as if reminding us that it's not done yet. Its summit is reached via a steep and exposed trail over frustratingly unstable volcanic scree; the round trip can take eight hours or more.

The 4,500-foot summit of Maderas Volcano can also be reached via a slightly less steep trail blessed with firmer footing and even some shade provided by trees and shrubs that have slowly reforested the slopes of this inactive volcano.

Find the best eggs Benedict at the Cornerhouse Café in Moyogalpa on Ometepe Island.

Ometepe is also home to a number of scenic waterfalls. The most popular, 160-foot-high San Ramon, is reached via a dirt road that was in such bad condition when I was there that I was advised against driving it even though I was traveling in a 4X4 truck. Once at the end of the road it's a further 2.5-mile walk to the waterfall over a rough and rocky trail. Your reward is an impressive cascade with an inviting swimming hole.

Get on a horse

A lower-impact way to explore Ometepe's natural attractions is on horseback. Hari's Horses ($8 per person per hour; www.harishorses.com), near the village of Balgue on the southeastern shore of the island, is owned by a guide and trainer named Hari who maintains a stable full of the most well-trained and well-fed horses I saw in all of Nicaragua. Hari offers scheduled and bespoke excursions for riders of all levels, including a four-hour trip to the San Ramon waterfall and a seven-hour ride around Maderas Volcano, which includes a swim in the lake with the horses.

Kayak at night

Ometepe's adventures don't stop when the sun goes down. Among the tours offered by Café Campestre in Balgue is a sunset kayaking trip in inflatable kayaks, which are extremely stable and increase your chances of getting close to birds and monkeys ($30 per person including equipment and guide; http://ometepe.moonfruit.com).

Cool off

Because Ometepe is a volcanic island I was worried that the Ojo de Agua swimming hole at the source of a natural spring might be heated by geothermal activity. Thankfully, the water at Ojo de Agua ($2 per person) is refreshingly cool and crystal clear — just right after a day of hot adventures.

Take a cultural adventure

Privately owned museums can sometimes be so personal that they have very little relevance for anyone else. Not so at El Ceibo museum ($4, including a guide in Spanish or English; www.elceibomuseos.com) just off the main road between Moyogalpa and Balgue. El Ceibo is actually two museums. One is focused on coins and money. The other is a memorable collection of pre-Columbian pottery, jewelry, petroglyphs and fascinating burial jars. Everything displayed in the museum, located in what used to be a tobacco drying barn, was collected on the still-working farm.

Play Tarzan

In Central America the term "canopy tour" has come to be associated with zip lines. However, Café Campestre will debut a true canopy tour in June during which guests will use looped ropes and ascenders to climb to the top of a 150-foot tall Ceibo tree. A portoledge has been placed in the upper branches of the tree, affording stunning views into and across the neighboring treetops and jungle canopy ($35 per person, two person max, including harnesses and guide; http://ometepe.moonfruit.com/).

Sustainable voluntourism

Visitors looking for a more immersive experience on Ometepe can choose from a number of voluntourism opportunities. Project Bona Fide Farm opened 12 years ago near Balgue and has grown into a ground-breaking permaculture operation, school and movement. Bona Fide has nearly 30 local staff members and up to 30 volunteers at a time who are housed and fed in exchange for work around the farm (www.startribune.com/a2023).

Volunteers are also welcome on the Organic Farm at Totoco Eco Lodge with a minimum commitment of one month spent weeding, planting and expanding the vegetable garden, increasing reforestation efforts, introduction honey bees and more ($4 per day per volunteer covers food and camping and dorm-style accommodation (www.startribune.com/a2022).

Writer Karen Catchpole and photographer Eric Mohl have spent more than five years on the road, traveling through North and Central America on their way to South America. Follow their journey at www.trans-americas.com.