Underneath New Zealand, deep down in the Earth's crust, there is hot melted rock called magma. In most countries it stays a long way underground. But in places like Rotorua, the magma is much closer to the surface, and it heats the rocks and groundwater above it.
When that hot water finds a crack to escape through, it shoots out as a geyser. The most famous one in Rotorua is called Pohutu, which means 'big splash' in Māori. It can shoot water 30 metres into the air - taller than ten storeys of a building.
All this volcanic activity sits along a line known as the Pacific Ring of Fire - a giant ring of volcanoes that runs round the edges of the Pacific Ocean. New Zealand sits right on it. So do Japan, Indonesia, the Philippines, and the western coast of the Americas.
Māori have lived around Rotorua for hundreds of years and learned to use the hot earth. They cook food in steam vents, soak in warm pools, and tell stories of the giants and ancestors who shaped the land. The geothermal earth is treated as a treasure to be looked after, not a curiosity to be poked at.