Undara Volcanic National Park

Undara sits about a five-hour drive inland from Cairns, well past where the rainforest gives way to dry savanna woodland, termite mounds and cattle stations that measure their size in hundreds of thousands of hectares rather than acres. I arrived expecting outback scenery and got that, but the reason to come is entirely underground: 190,000 years ago, one of Australia’s youngest volcanoes erupted here with such fluid, low-viscosity lava that instead of building a cone, it flowed for over 160 kilometres, the outer surface cooling and crusting over while the molten rock kept moving beneath, eventually draining away and leaving hollow tubes behind. It’s one of the longest lava flows from a single volcanic eruption known anywhere on the planet.

You can’t explore the tubes without a guide, which turned out to be the right call rather than a bureaucratic inconvenience — the entrances are through collapsed sections called “the Archways,” where the tube roof caved in millennia ago and rainforest microclimates now grow inside the sinkholes, fig trees and ferns thriving in the constant humidity thirty metres below the surrounding dry savanna. Walking from blinding outback sunlight into that pocket of green, then further in to where the tube proper begins — smooth basalt walls, a ceiling still marked with the flow lines from the original lava, bats roosting in the darker sections — was one of the stranger transitions I’ve made between two completely different ecosystems within the space of about fifty metres.

The tubes are also home to thousands of microbats and, near the entrances at dusk, the little red flying foxes and bent-wing bats stream out in numbers dense enough to blur against the darkening sky, hunting insects over the surrounding grassland. I stayed at the lodge on-site, in one of the old railway carriages converted into rooms, and sat out with a beer watching that nightly exodus until it was too dark to make out individual shapes.

The surrounding savanna, part of the vast Undara Volcanic Park estate, is worked cattle country still, and the isolation is real — this is the kind of outback silence that makes you understand instantly why the night sky out here looks the way it does, with no ambient light for a hundred kilometres in any direction.

When to go: May through September, the dry season, is the only realistic window — roads can flood and close in the wet, and the heat becomes oppressive by November. Book the guided cave tours ahead; numbers are limited and it’s the only legal way in.