Þingvellir National Park, Iceland

Pingvellir National Park is where democracy was born in 930 AD when the first Parliament in the world, the Althing, assembled here for the first time. The Law Speaker used to read out new laws every year from the Law Rock here (a tradition that has only remained at Tynwald on the Isle of Man - a place where the oldest continuous Parliament still gathers annually). It met here until 1789 when an earthquake caused the Parliamentary Plain to slip by a metre (3 ft) and the Parliament was moved to the current capital, Reykjavik.
The Pingvellir National Park consists of the Parliamentary Plains, the rift valley and the Lake Pingvallavatn.
114-m deep Lake Pingvallavatn is very rich and diverse in vegetation and fish species due its location on top of a new lava, full of minerals that are absorbed by the water. The porous lava also creates lots of hideaway places for fish. Lake Pingvallavatn is also the largest lake in Iceland at 84 sq km (32 sq mi). The Lake gets its water from Langjokull glacier and it takes the water 20-30 years to get from the glacier to the lake through underground channels, as well as the rain in the lakes catchment area which takes 2-4 months to reach the lake. Just south of the Lake Pingvallavatn lies Nesjavellir - the hottest area in the country. Reykjavik Energy uses the water that gets heated up by the hot rocks to harness hot water and to generate electricity.
The rift valley between the North American and Eurasian plates increases in size by 2 cm a year, meaning that along with Great African Rift Valley it is one of two places in the world where major plate drifting apart can be observed. It is part of a Mid-Atlantic ridge fissure zone running diagonally through Iceland, pulling it apart and increasing it's size every year. You can walk or swim through the faults and fissures in the area, the most famous being Almannagja that leads along the North American plates eastern side to Oxararfoss waterfall.
Pingvellir National Park is significant both historically and geologically, no wonder it has been included into UNESCO World Heritage Site list. But it's natural beauty can't be forgotten too, either you travel there in summer o winter, it's spellbinding beauty won't leave anyone indifferent. And just like the rest of Iceland, it will leave you craving for more.