The original site of the city lay upon a hill overlooking a lake, settled sometime during the Paleolithic Period and later by a tribe of Ligurian and pre-Celtic peoples. Around 500 BC Geneva became a fortified town inhabited by the Celts before it was taken by the Romans in 121 BC. Ownership of the city continued to flip between the warring neighboring states, before landing in the hands of the German Emperor in 1033 AD. By this time Geneva had become an important ecclesiastical seat, with the bishop of the city a direct vassal of the Holy Roman Emperor as a territorially vested prince.
Power of Geneva was contested between the nearby Savoy dukes and the Catholic bishop for the next five centuries. When the last ruling bishop fled the city in 1533, the citizens of Geneva made a risky move in an attempt to rid themselves of both the Catholic rule and the Savoyards - the city allied itself with the Protestant state of Bern and declared themselves a Protestant sovereignty in 1536. While this did give power back to the people of Geneva, it also alienated the city from the surrounding Catholic Swiss population for generations. The Protestant reformationist John Calvin came to reside in the city shortly thereafter in 1536 and stayed for the next thirty years until his death, becoming a new spiritual leader in the absence of the bishop. The city remained a stronghold of the Protestant faith for many years to come, although a large section of the historic section reverted back to Catholicism by the early 17th century.
Geneva was briefly annexed by France during the French Revolution, but in 1814 it was admitted into the Swiss Confederation at the Congress of Vienna, its jurisdiction expanded to cover the fifteen neighboring Savoyard parishes. The Congress expressly provided that these Catholic Savoyard parishes would be protected from religious persecution, and in return, guaranteed the city's own neutrality. Tensions continued to run high between the Catholics and Protestants until 1907 when Geneva passed a law mandating the official separation of Church and State - no religious body has received aid from a state or municipal power since.
After World War I Geneva became the seat of the League of Nations in 1919, giving it the status of "the international city". Its new reputation continued after World War II when the European headquarters of the United Nations was seated in the city, bringing along with it numerous other international bodies and organizations. Tourism and business have thrived in the city since.