The Tunnel books (also called peepshow books) contain a set of pages bound with two folded concertina strips on all side and viewed through a hole in the cover. Openings in each page let the onlooker to make out through the complete book to the back, and images on each page work together to create a dimensional sight inside the book. This book type dates from the mid-eighteenth century and was enthused by theatrical stage sets. By tradition, these books were often created to commemorate particular events or to be sold as souvenirs of tourist attractions. (The term "tunnel book" was derives from the truth that many of these books were made to remember the building of the tunnel under the Thames River in London in the mid-1800's.) In United States, the tunnel books were useful for such attractions as like World Fairs and the New York Botanical Gardens.