The earth heaves up boiling water and steam, and from these mist coalesces, drifts with the light wind. We walk out over the simmering pools lined with vibrantly coloured minerals and flecked with obsidian, giving the basin its name. Vapour rises all around us. Every now and again, a burst of trapped air escapes, jetting sprays of searingly hot water well above our heads, and fortunately well away from the viewing platform built right over the bubbling land.