It's where Pele lives, her hair streaming high over the south of Big Island.
The current eruption began a year or so ago, with an ash and steam cloud pushed west by the trade winds. The lava began to rise, filling the bottom of the crater, and pooling to about 300 m below the surface. The resulting sulphur dioxide levels have meant that much of the caldera loop road is closed - but you're still able to get out to the Jaggar Museum, where there's a viewing area.
In the day, all you can see is the plume of smoke, rolling off the west.
At night, everything is different, as the glow of the lava in the vent colours the plume, and reflects of the walls of the crater. It's an eerie experience. Strange patterns whirl around the illuminated plume, as the orange glow shines across smooth lava of the caldera floor.
I found a rock in the viewing area and set up a long exposure.
First I took a few shots of the wider caldera, catching some of the night sky.
Then I zoomed in.
Yet more geology in action.