Of the two natural islands located within the Seine River of Paris, the Île St. Louis is the lesser known when compared to the Île de la Cité; however, the Île St. Louis is not without its own special charms. The island gets its name from King Louis IX, and has a much more tranquil air about it than its sister island. The majority of the island is comprised of residential buildings, and even though it is connected on both sides to the banks of the Seine by bridges, there is very little traffic into and out of the island. If you were looking for a peaceful place to spend a day, the Île St. Louis would be a good trip to plan, as there are a number of quiet cafés and restaurants, and some beautiful streets for strolling along. The largest building on the island is the Saint-Louis-en-l'Île Church, which dates back to the late 17th century, and is a fine place to take in some of the architectural history of Paris, without the hustle and bustle of downtown.