Zurich is the largest city in Switzerland and the capital of the canton of Zürich. It is located in north-central Switzerland at the north western tip of Lake Zürich. The municipality has approximately 400,028 inhabitants, the urban agglomeration 1.315 million and the Zürich metropolitan area 1.83 million. Zürich is a hub for railways, roads, and air traffic. Both Zürich Airport and railway station are the largest and busiest in the country. Permanently settled for over 2000 years, Zürich was founded by the Romans, who, in 15 BC, called it Turicum. However, early settlements have been found dating back more than 6400 years ago. During the Middle Ages, Zürich gained the independent and privileged status of imperial immediacy and, in 1519, became a primary centre of the Protestant Reformation in Europe under the leadership of Huldrych Zwingli. The previous boundaries of the city of Zürich (before 1893) were more or less synonymous with the location of the old town. Two large expansions of the city limits occurred in 1893 and in 1934 when the city of Zürich merged with many surrounding municipalities, that had been growing increasingly together since the 19th century. Today, the city is divided into twelve districts (known as Kreis in German), numbered 1 to 12, each one of which contains between one and four neighbourhoods. The official language of Zürich is German, but the main spoken language is the local variant of the Alemannic Swiss German dialect, Zürich German.