Prague is classified as an "Alpha-" global city according to GaWC studies and ranked sixth in the Tripadvisor world list of best destinations in 2016. In 2019, the city was ranked as 69th most liveable city in the world by Mercer. In the same year, the PICSA Index ranked the city as 13th most liveable city in the world. Its rich history makes it a popular tourist destination and as of 2017, the city receives more than 8.5 million international visitors annually. In 2017 Prague was listed as the fifth most visited European city after London, Paris, Rome and Istanbul.