What lies beneath: step into 10 of Australia's most spectacular caves

In East Gippsland at the Buchan Caves, the Parks Victoria-led tours of Royal Cave and Fairy Cave focus on the twinkling decorations in what was once a coral-filled sea. The limestone formations on show include grand stalagmites and stalactites, pools lined with calcite, plus all manner of strange bulges. Half the fun comes in working out what the weird outcrops look like. One unusual difference here is that the caves are within a wider reserve, laced with forest walking trails and hosting a fairly rustic campground. parks.vic.gov.au

To thoroughly gorge on caves, the Margaret River region of south-western WA is the place to go. There are several here, with Mammoth Cave - deep inside the Boranup Karri Forest - having the biggest cavern. The scale comes with an impressive fossil haul. The bones of several long-extinct creatures have been found inside the cave, with many of the megafauna bones displayed in cases within the cave. One key fossil is still in the cave wall, however. The jawbone of the zygomaturus - otherwise known as the giant wombat - has been there for 50,000 years. capesfoundation.org.au

The experience at the Capricorn Caves, 23km north of Rockhampton, can be tailored to taste. If you just want a really big, impressive cave that the whole family can ooh and ah at, then the tour of Cathedral Cave should do the trick. More adventurous types, however, can wriggle their way through the narrow passages and snaking tunnels, with a head torch guiding the way. The Capricorn Adventurer tour is intentionally challenging, adults only and offers a good introduction to caving. Just accept that you're getting dirty. capricorncaves.com.au

Australia's best-known caves - the Jenolan Caves west of the Blue Mountains - are currently closed due to road damage. But there are plenty of other options in NSW. Inside Kosciuszko National Park, six visitable caves lie within a 440-million-year-old belt of limestone. Of the Yarrangobilly Caves, South Glory impresses with sheer size, and is open for self-guided visits. To see the ultra-rare black flowstone of Jersey Cave or the dramatic shawls of Jillabenan Cave, however, you'll need to join a tour. The caves are pretty darned chilly year-round, but you can warm up by jumping into the neighbouring spring-fed Yarrangobilly Thermal Pool, which stays at 27 degrees all year round. nationalparks.nsw.gov.au

Most cave systems come through the gradual compression of limestone, but the Undara Lava Tubes in northern Queensland's Gulf Savannah region come courtesy of a volcanic eruption. The tubes were created when a crust formed around liquid lava that flowed away, leaving a hollowed-out effect. Undara has the most extensive collection of lava tubes in the world, with the system stretching for 160km. Don't expect graceful iceberg-esque formations - Undara's vibe is giant black tunnels and the bats that live within them. undaralavatubetours.com.au

In the Mole Creek Karst National Park of north-central Tasmania, Marakoopa Cave ticks off a marvellous checklist of subterranean treats. The stalagmites and stalactites are both plentiful and colourful, while the underground creeks are reflective and eerily noisy. But the stars of the show here are the glow worms. Thousands of them line the cave walls and roof, twinkling away like a night sky. Just don't spend too much time thinking about what those glow worms are - decidedly less romantic gnat larvae. parks.tas.gov.au

If WA's Mammoth Cave is all about the size and fossils, Lake Cave majors in decorations. The stairs head down inside a large sinkhole, and the stalactites and crystal formations start lining up shortly afterwards. The centrepiece of Lake Cave is an underground lake, which has mirror-like reflective qualities. The main thing you'll see in it is the hefty table-like formation that hangs above it. But wait for the droplets coming down from the cave roof, plink-plonking into the water and creating a ripple effect. capesfoundation.org.au

Having spent 500,000 years as a giant pitfall trap, the cave system at Naracoorte has earned its place on the UNESCO World Heritage List by collecting an extraordinary wealth of fossils. Four of the 28 caves discovered so far are open to visitors, but the truly important one - Alexandra Cave - can only be seen on guided tours. The guide helps bring the backstory to life, though. The fossil record here comes in layers, covering several ice ages and charting the arrival of humans on top of the long-gone megafauna. naracoortecaves.sa.gov.au

The caves at Mount Borradaile in the permit-only Arnhem Land aren't deep - most are essentially rock overhangs. The extraordinary decoration is not nature's work either. But the concentration of Aboriginal rock art in this part of Australia is unparalleled. The galleries feature multiple overlapping layers of art, with the oldest contributions going back 50,000 years. The single most arresting sight, however, is the six metre-long depiction of the Rainbow Serpent, which has been given very sharp, almost crocodilian teeth. Davidsons Arnhemland Safaris has a lodge at Mount Borradaile and offers guided rock art tours. davidsonsarnhemland.com.au

The vast majority of caves around the South Australian outback town of Coober Pedy are man-made. Most inhabitants of this remote opal-mining hotspot choose to live in dug-out homes to protect them from the ferocious heat. Visitors can tour show homes and admire the intricately carved Serbian Orthodox Church. But best of all, they can stay underground, too. The Desert Cave Hotel has subterranean rooms where comfortable beds are surrounded by exposed rock - and those walls and ceilings have some remarkable, blood-like red mineral streaks within them. desertcave.com.au