Costa Rica has spent four decades building an adventure industry, and the commercial canopy tour — travelling through the forest suspended from steel cables — was invented here, in Monteverde, as a method of canopy research before it became an attraction.
Zip lines
They exist across the country, but two areas stand out. Monteverde has the longest and most spectacular runs, some over a kilometre above the clouds, with rappel descents between platforms. Arenal combines lines with views of the volcano and the lake. Prices are broadly similar; what varies is safety and maintenance, so choose established operators rather than the cheapest sign in town.
Rafting
The Pacuare river ranks among the best rafting rivers in the world. Its class III and IV rapids run through a primary rainforest canyon beside Cabécar indigenous territory, with waterfalls dropping straight into the river. It can be done as a long day from San José or Turrialba, or as two days with a night at a road-free lodge inside the canyon, which is the version worth taking.
For anyone not seeking adrenaline, the Sarapiquí has class II and III sections, and the Peñas Blancas is floated gently for wildlife watching.
Río Celeste
In Tenorio Volcano National Park, the Río Celeste is a turquoise that looks edited in photographs and is not: it forms where two colourless rivers meet and suspended aluminosilicate particles reach exactly the size that scatters blue light. The trail to the waterfall and the teñidero takes about three hours return, with mud effectively guaranteed.
Important: the colour depends on recent rain. After heavy storms the river clouds and loses its blue for days.
Other activities
Canyoning on the waterfalls near La Fortuna, hanging bridges, rappelling, diving at Caño Island and — for experienced divers — Cocos Island, 550 kilometres offshore, reachable only on week-long liveaboards and famous for its schooling hammerheads.
Safety
The sector is regulated but standards vary. Ask about the operator's certification, check that equipment looks well maintained, and be wary of prices far below the market. Your travel insurance must cover adventure sports explicitly: many standard policies exclude them.
What to wear
For any of this, assume you will get wet and muddy. Quick-drying clothing, footwear you can soak, and a dry bag for phone and documents are the basics. Waterfall and canyoning trips normally supply helmets, harnesses and wetsuits where needed. Leave watches and loose jewellery behind — zip lines and river trips lose them routinely.