Founded in 1536 by the Spaniard Pedro de Mendoza, for a century and a half Buenos Aires was cut off from the main routes of South America, only gaining importance in the 18th century. As the capital of the Viceroyalty of the RÃo de la Plata, Buenos Aires saw a large influx of European immigrants in the 19th and 20th centuries. With its wide tree-lined avenues, impressive buildings, and cosmopolitan atmosphere, Buenos Aires is considered one of the most beautiful cities in South America. The Argentine capital has a more European than South American atmosphere and is characterized by lively streets, luxurious boulevards, old-style cafes, and classy restaurants. Buenos Aires is rich in history, culture, and must-see attractions, starting with its colorful neighborhoods and the historic city center, which is the nerve center of the city's relationship with politics.