16 million day-trippers visiting the city every year. The number of visitors has been growing steadily over the past decade. This can be attributed to an increasing number of European visitors. Two-thirds of the hotels are located in the city's centre. Hotels with 4 or 5 stars contribute 42% of the total beds available and 41% of the overnight stays in Amsterdam. The room occupation rate was 85% in 2017, up from 78% in 2006. The majority of tourists (74%) originate from Europe. The largest group of non-European visitors come from the United States, accounting for 14% of the total. Certain years have a theme in Amsterdam to attract extra tourists. For example, the year 2006 was designated "Rembrandt 400", to celebrate the 400th birthday of Rembrandt van Rijn. Some hotels offer special arrangements or activities during these years. The average number of guests per year staying at the four campsites around the city range from 12,000 to 65,000. De Wallen (red-light district) De Wallen, also known as Walletjes or Rosse Buurt, is a designated area for legalised prostitution and is Amsterdam's largest and best-known red-light district. This neighbourhood has become a famous attraction for tourists. It consists of a network of canals, streets, and alleys containing several hundred small, one-room apartments rented by sex workers who offer their services from behind a window or glass door, typically illuminated with red lights. In recent years, the city government has been closing and repurposing the famous red-light district windows in an effort to clean up the area and reduce the amount of party and sex tourism. Retail Shops in Amsterdam range from large high-end department stores such as De Bijenkorf founded in 1870 to small speciality shops. Amsterdam's high-end shops are found in the streets P.C. Hooftstraat and Cornelis Schuytstraat, which are located in the vicinity of the Vondelpark. One of Amsterdam's busiest high streets is the narrow, medieval Kalverstraat in the heart of the city. Other shopping areas include the Negen Straatjes and Haarlemmerdijk and Haarlemmerstraat. Negen Straatjes are nine narrow streets within the Grachtengordel, the concentric canal system of Amsterdam. The Negen Straatjes differ from other shopping districts with the presence of a large diversity of privately owned shops. The Haarlemmerstraat and Haarlemmerdijk were voted best shopping street in the Netherlands in 2011. These streets have as the Negen Straatjes a large diversity of privately owned shops. However, as