Sima de las Cotorras

The sima is a perfect wound in the limestone: a collapse sinkhole 160 metres across and 140 deep, its sheer walls dropping to a disc of self-contained rainforest on the floor - and, for most of the year, it functions as a green volcano. Thousands of Mexican green parakeets roost in the walls, and at first light they erupt: flocks spiraling up the cylinder in shrieking gyres, circling the rim and scattering to the day's feeding, the show reversing at dusk when they pour back in like water down a drain. The ejido of Piedra Parada runs the site with cabins, a comedor and the rim trail - which adds the second wonder: dozens of red rock paintings, hands, figures and suns, made by ancient Zoque people on a ledge partway down the sheer wall, visible from viewpoints and reached today only by the guided rappel that also lets the adventurous descend to the sunken forest floor. Between flights, hummingbirds and motmots work the rim scrub and the El Ocote reserve rolls to the horizon.

What you actually see

• The dawn eruption - parakeet gyres up the sinkhole cylinder.
• The rim circuit - the full 160-metre mouth from above.
• The rock paintings - ancient red figures on the sheer wall.
• The rappel - the descent to the sunken forest for the qualified.

When to go

February to October, when the parakeets are present - they largely vacate from November to January; be on the rim before sunrise or an hour before dusk. Overnighting in the cabins makes both shows easy.

Honest expectations

The spectacle keeps bird hours - miss dawn and the sima is a beautiful hole. Rappelling requires booking and nerve. Facilities are ejido-simple and cash-only.

Nearby

The El Aguacero waterfall descends its canyon minutes away; Tuxtla and the Sumidero boats lie an hour east.