Vatican forced to tighten security at the Sistine Chapel after pickpockets target huge crowds of tourists Official guides have threatened to go on strike if security is not improved Tourists are writing about their experiences on websites including TripAdvisor Some 25,000 people visit the chapel in Vatican City everyday Tourists craning their necks to admire the artwork by Michelangelo in the Sistine Chapel are being targeted by thieves taking advantage of the crowds. Holidaymakers have been leaving warnings on travel websites urging others not to get stung when they visit Vatican City. It has prompted calls for the Vatican to improve security and restrict the number of visitors it lets in during the day. Tourists craning their necks to admire the Sistine Chapel are being pick-pocketed by thieves taking advantage of the crowds Official guides have even threatened to go on strike if something is not done. A similar protest recently took place at the Louvre, in Paris. Holidaymakers are now writing about their experiences on websites including review site TripAdvisor. One wrote: 'Of the many places visited in Rome, we felt vulnerable at the Vatican.' Angela Bolton, a guide from Kent, told The Times: 'The situation is getting out of hand. The Vatican lets in as many people as they can. Up to 30,000 people have been going through the museum on a single day, which means crowds like those on the Tokyo Underground. The Sistine Chapel, or Cappella Sistina in Italian, takes its name from the man who commissioned it, Pope Sixtus IV. Some 25,000 people a day, or five million people a year, visit the chapel which is the best-known chapel of the Apostolic Palace, the official residence of the Pope in the Vatican City Some 25,000 people a day, or five million people a year, visit the chapel. Entry to the Vatican Museums and Sistine Chapel costs €16, earning the Vatican an annual revenue of around €80 million or £70 million a year. Sisto conducted his first Mass in the chapel on August 1483. The Sistine Chapel is most famous for Michelangelo's frescoes, but long before Michelangelo, Sisto commissioned painters such as Botticelli to fresco the two long walls of the chapel. One side told the story of Moses, the other the story of Christ. Even without Michelangelo's work, these earlier paintings still represent one of Europe's greatest fresco cycles. Michelangelo began work on the ceiling in July 1508. The completed frescoes were unveiled in October 1512.