Geysir (the Icelandic original, after which all others were named) no longer gushes all that often, but just a few metres away is his son Strokkur who faithfully erupts every 4-6 minutes. He even offered some double-spews and triple-spews. He is said to shoot up to 20m high, but it looks higher to me, if I can judge 20m in relation to the observers standing by. Watching Strokkur shoot his stuff gave me the same exhilarating WHEEEEEEE! feeling of riding a roller-coaster.