The touristic circuit of Iceland, very accessible from Reykiavic are the most visited sites of the country THINGVELLIR, GEYSIR and GULFOSS. This combo is easily done in one day.
The national park of Thingvellir
It is a UNESCO World Heritage Site. This is where the border between Europe and America is located. This is also where Iceland's first parliament was held. The landscape is restful. You will be able to discover the lake of Pingvallatn, the Sifra fault (diving spot) and the Oxararfoss waterfall.
Geysir
Here are concentrated several Geysers, the smallest one is called Strokkur it gushes out at 20m every 10/15min. The biggest one, which gave its name to the place, gushes out at 60m but only a few times a year.
Gullfoss
Waterfalls 32m high. Very impressive, they owe their name "golden falls" to the rainbow that appears on clear days.
The Blue Lagoon
To finish our day we go to the Bluelagoon. We had chosen to do it at the end of the day to avoid the crowd, and enjoy this turquoise blue water heated to 40°. Bad luck for us at 1h from closing time we are told that the lagoon is full ... time to take some pictures but no swimming for us ... at the same time under the rain and with the crowd it saves us 40e. Let's stay positive !