The geyser all geysers are named after just happens to be in Iceland and it's part of the Golden Circle.
The spouting hot water jet of Geysir, aka The Great Geysir, is an iconic image, and before cheap flights to Iceland allowed foreigners to really begin discovering the country properly it was one of the only pictures of Iceland you would find on Google (or whatever search engine people were using back in the 1940s and 50s).
So iconic – not to mention unusual – is The Great Geysir that the name was transposed almost directly to English as geyser and used to describe all such phenomena everywhere. This is because it was the first geyser Europeans had ever seen and incidentally it was the first geyser ever described in a printed source.
Geysir is located in a place called Haukadalur Valley, which is famous for all sorts of geothermal springs, pools and geysers in a very small area. It is all very interesting indeed; and that’s just as well because you’ll be very, very lucky to see the Great Geysir itself erupt while you’re there.
Although geology seems improbably permanent by human standards, in Iceland it really isn’t. Any one of our regular volcanic eruptions could see a new mountain or island created from nothing. The Great Geysir, for example only erupted for the very first time (that any human saw) in the 1300s and many others have come and gone all over the country. These days if you want to see Geysir spout boiling water up to 70 metres into the air you’ll need an earthquake or a lot of patience. It does erupt; but very infrequently, sometimes with a few years in between.
Not to worry though. Its slightly smaller cousin, Strokkur spouts equally scalding water up to 30 metres high every few minutes and has been doing for years. Strokkur is located just 50 metres away.