There are some things you never think you'll encounter while travelling, such as the fire and brimstone offered as torment to the ungodly in the Old Testament's more excitable verses. The sort of thing you see in church frescoes, where sinners are being thrust into bubbling cauldrons by horned devils with pitchforks.
No one is being tossed into the brew at Wai-O-Tapu, but there's plenty of fire and brimstone, which is an archaic word for sulphur. One of the pools is called the Devil's Bath and is filled with lime-green mud that would peel your skin off. It owes its cartoonish colour to sulphur and ferrous salts that rise up through the earth's bowels, bringing with them the stench of hell itself. Or so you might imagine, because this bizarre landscape leaves you with few other references.