Undara is very similar to Cobbold Gorge (last post but one) in that it is a privately-owned tourist operation showcasing a spectacular geological formation in the middle of what was once a cattle station in the Gulf country. We had two nights at each and would have been happy with longer.
Both places offer various levels of accommodation from campsites up to comfortable huts, with bar and restaurant facilities, etc. Both also offer a range of self-guided walks as well as guided tours. At Undara the whole of the cattle station except the camp area, the Lodge, became National Park, whereas only a small part of the cattle station around Cobbold Gorge was protected. This difference is more theoretical than practical, however, since wandering around trackless Gulf savannah country is not a good idea anyway, however beautiful it may look at sunset.
The main feature at Undara is the Lava Tube formation, a fan of tunnels formed when lava spread slowly across the landscape 190 000 years ago. The stats (Wikipedia) are impressive: 23 billion cubic metres of lava released, flowing up to 160 km from the vent and forming tubes up to 100 km long. The tubes have gradually been interrupted by roof collapses and silting, but the collapsed sections have become sheltered pockets of green vegetation, “vine thickets”, important refuges for plants and wildlife.
The walks around the Lodge take half an hour to half a day and lead the visitor along the edge of a swamp and up on to the ridges for a good look at the wildlife (wallabies; lots of birds; insects) and plants (wattles, paperbarks and grevilleas in full flower when we we there; kapok; bottle trees) but there was no real need to go far: we saw three different macropods around the campsite as well as an emu and more small birds than we could count (photos later).