Golden Circle & Secret Lagoon Tour

Kerið is a volcanic crater about 270 metres long, 170 metres wide and 55 metres deep, with a blue-green lake at the bottom. Unlike the black basalt found almost everywhere nearby, its walls are deep red, from oxidised volcanic rock. It is thought to have formed when a magma chamber emptied and the ground above collapsed, rather than in a violent explosion. You can walk the rim and, where allowed, down to the water. There is a small entry fee. You can walk the rim on a paved path or take the steps down to the water.

The Secret Lagoon, also called Gamla Laugin, 'the old pool', in Flúðir, was built in 1891 and is Iceland's oldest swimming pool, restored and reopened to visitors in 2014. It keeps a natural feel: a stone-edged pool set into a geothermal field, with steam drifting off water that stays at 38 to 40°C all year. A small geyser, Litli Geysir, erupts beside the pool about every 5 minutes.

Geysir gave every geyser in the world its name. The original Great Geysir now erupts only rarely, sometimes after earthquakes, so the show is Strokkur, a short walk away. It throws boiling water 15 to 20 metres into the air every 5 to 10 minutes, and sometimes a good deal higher, so you will see several eruptions while you are here. Keep to the paths between the pools and stay behind the ropes, as the water is very hot.

Gullfoss, the Golden Falls, drops about 32 metres in two steps into a narrow canyon roughly 70 metres deep and 2.5 kilometres long. The water comes from the Hvítá river, which is fed by the glacier Langjökull. Glacial water often turns golden-brown in sunlight, and rainbows hang in the spray on bright days. A path with stairs leads down to a lower level, closer to the water.

Þingvellir is where Iceland's parliament, the Alþingi, first met in 930, and it lies in a rift valley where the North American and Eurasian plates are pulling apart. Chieftains gathered here every summer, laws were recited from the Lögberg (Law Rock), and the plain below still shows where the assembly booths stood. The lake beside it, Þingvallavatn, is the largest natural lake in Iceland. The park is free to enter and open all year.