While religious tourism often takes the form of lengthy group trips, in other instances it can take the form of a day trip or a brief visit to a holy site. There are many locations throughout Europe, Africa, Central and South America that are regarded as holy by some Christians because people claim to have seen visions of religious figures at these sites. During religious holidays and celebrations, many people from the surrounding areas visit these sites and religious ceremonies are held to mark particular occasions. Similarly, Muslims, Buddhists, Hindus and believers in other faiths often embark on brief pilgrimages to holy sites in Saudi Arabia, India or other parts of Asia. Therefore, religious tourism can involve both formal travel arrangements or impromptu trips to nearby sites.