The two scenic spots of Þríhnúkagígur and Leitin are found near Reykjavík. The former is a crater with an empty magma chamber underneath. Now it is possible to enter the resulting cave, one of its kind in the world. The second is a crater very few people visit, but the lava from it created the Raufarhólshellir lava tube, known as the Lava Tunnel in tourism. It also created Rauðhólar pseudocraters and Tröllabörn hornitos in the same eruption, over 5000 years ago. Both craters are found along the mysterious 64th parallel.
.https://en.wikipedia.org/wiki/Thrihnukagigur
.https://en.wikipedia.org/wiki/Leitin
