Þingvellir is the one place in Iceland where geology and history are inseparable. The national park sits in a rift valley, a wide, grassy trough bounded by cliffs, where the North American and Eurasian tectonic plates are slowly pulling apart. You can walk between the walls of the fissure and feel the gap, and in the lake beside it divers swim between continents.
In 930 the Icelandic chieftains gathered here for the first time to form the Althing, one of the oldest parliamentary institutions in the world, and for the next nine centuries the assembly met on the plain each summer. Laws were recited from the Lögberg, the Law Rock, and disputes were settled, feuds were stopped or started, and people from all over the island camped in turf booths. In 1000 the Althing voted to adopt Christianity, a decision that shaped the country. The site is a UNESCO World Heritage site, and for Icelanders it is a place of deep national feeling.
The riding approach is pleasant, with the road climbing from the coastal plain and then descending to the lake of Þingvallavatn, the largest natural lake in the country. The bends are gentle and the surface good, but the traffic can be heavy in summer, and the car parks fill up. Early morning is the best time, when the light is low and the crowds not yet there.
Nature is full of detail. The lake is fed by cold clear springs, and the water is so clear that visibility under the surface is extraordinary. Birch scrub and moss-covered lava cover the ground, and the Öxará river drops into the rift at the waterfall of Öxarárfoss. Birds nest in the cliffs, and the smell of damp moss and cold water is strong.
Services near the park are limited to a visitor centre and basic facilities, so Reykjavík and the town of Selfoss are the main centres for supplies. Wind off the lake is strong, so dress for a chill even in July.