The most famous day trip from Reykjavik and deservedly so, as it combines history, geology, waterfalls and geothermal activity, pretty much Iceland in a nutshell.
Where the original Icelandic parliament, one of the oldest in the world, would meet for a fortnight each year. It’s also where America and Europe literally meet, one of only two places in the world (the other is the Great Rift Valley in East Africa) that continental drift between tectonic plates can be seen. Both those facts I knew before I went but I had no idea what the place looked like or how staggeringly beautiful it would be.
Where the word Geyser came from, an interesting collection of geothermal sights, not as colourful or extensive as those at home in Rotorua, but still pretty impressive, particularly the geyser erupting.