Þingvellir National Park (pronounced Thingvellir) is about 30 miles east of Reykjavík. The 50 square-kilometer park was created in 1928 and is Iceland's most historic site. The oldest existing parliament in the world first met here in 930AD. The Alþing met here every year to enact laws, including the law passed in 1000AD to introduce Christianity into the island. 

The park building has interactive displays that show the history and ecology of the area. Iceland is on the North Atlantic Ridge that stretches between the poles mostly under the Atlantic Ocean. The slow separation of North America and Eurasia on this ridge has created Iceland and the movement is why the country continues to grow larger - from the middle. The distance between the walls in the park building represents the distance the continents have moved apart since the area was first used in the 900s.

Lögberg is the cliff overlooking the place where the Alþing (assembly) met, and speakers stood to address gatherings. 

Öxarárfoss waterfall on the river Öxará in Almannagjá, a lava gorge.

Nearby on the river Öxará is Drekkingarhylur (The Drowning Pool), where mothers of illegitimate children were drowned.

Þingvallavatn (Thingvallavatn) is the largest lake in Iceland, 83sq km (32sq miles) and over 100m (328ft) deep. Only a few small rivers feed the lake. Most of the water inflow is from underground sources. This lake feeds Iceland's largest spring fed river, the Sog River, which supplies energy to three hydroelectric poser stations creating almost 90 MW of electricity. The lake offers excellent arctic char and trout fishing. No motorized boats are allowed on the lake.

 Nearby is Valhöll (Valhalla), a hotel and restaurant that open for the summer months only. The food is wonderful!