The Gullfoss is a waterfall in the Hvítá river. It is, just as Þingvellir National Park (day 9) and Geysir/Strokkur, part of the Golden Circle; a famous tourist route starting from Reykjavik. This makes Gullfoss one of the most famous Icelandic tourist spots. It is a dual step waterfall with many different viewpoints, so you can see the waterfall from different angles.