Great Geysir, Geyser in Haukadalur valley, Bláskógabyggð, Iceland

Great Geysir is a hot-water pool geyser in Haukadalur Valley, Bláskógabyggð, on the eastern slopes of the Laugarfjall rhyolite lava dome. Its funnel-shaped conduit, 0.4 to 1.0 m wide and about 23 m deep, narrows before branching into cavities below 16 m. Eruptions hurl boiling water up to 60 m, but are now infrequent and can pause for years.

The first known written mention dates from 1647, when travelers described the hot springs of the valley. An earthquake in 1896 caused increased eruptions that sent water columns as high as 80 meters (about 260 feet) into the air.

The name comes from the Icelandic verb geysa, "to gush", and was first recorded for this spring in 1647, when bishop Brynjólfur Sveinsson described it. The word then spread to other languages for similar hot springs. Visitors today usually watch the nearby Strokkur erupt every few minutes, while Geysir itself is mostly dormant.

The geothermal area is freely accessible all year round and sits about a two-hour drive from Reykjavík. The paths around the hot springs are marked, but the stones can become slippery when wet.

The fumaroles leave yellow sulfur deposits on the rocks around the springs, which can appear orange or greenish depending on the light. Some thermal springs form shallow pools of turquoise water that, despite the appealing color, are close to boiling temperature.