Iceland. Geysir (sometimes known as The Great Geysir), in the Haukadalur valley, is the oldest known geyser and one of the world's most impressive examples of the phenomenon. The english word geyser to describe a spouting hot spring derives from Geysir (which itself is derived from the Icelandic verb gjosa meaning to erupt). Geysir lies on the slopes of Laugarfjall hill.