Bruarhlod (Brúarhlöð) canyon is one of those less known gems that many tourists miss out on seeing, despite it lying conveniently close to Þingvellir and other Golden Circle locations.
Nearby places: Gullfoss, Geysir, Secret Lagoon
This place is known for its extraordinary rock formations that look phenomenal when seen from the top of the canyon. The rock formations are made of Breccia, which is a rock composed of broken fragments of minerals or rock cemented together by a fine-grained matrix.
It can be similar to or different from the composition of the fragments; and at Brúarhlöð, it was formed by tectonic and volcanic forces, which gives the gorge its unique look.
Here´s a great article about Brúarhlöð on the website of Reykjavík Grapevine