Reykjavik, Iceland’s coastal capital, is renowned for the late-night clubs and bars in its compact center. It's home to the National and Saga museums, tracing Iceland’s Viking history. The striking concrete Hallgrimskirkja church and rotating Perlan glass dome offer sweeping views of the sea and nearby hills. Exemplifying the island’s dramatic landscape is the volcanic setting of the geothermal Blue Lagoon spa. Reykjavík is believed to be the location of the first permanent settlement in Iceland, which, according to Ingólfur Arnarson, was established in AD 874. Until the 19th century, there was no urban development in the city location. The city was founded in 1786 as an official trading town and grew steadily over the next decades, it is among the cleanest, greenest, and safest cities in the world. Despite its northern latitude, temperatures very rarely drop below −15 °C (5 °F) in the winter. Summers are cool, with temperatures fluctuating between 10 and 15 °C (50 and 59 °F), rarely exceeding 20 °C (68 °F).