Peep-show of engineering marvel
Originally a foot tunnel, it was converted to railway use in 1869, and eventually became part of the London Underground.
This folding paper peep show enables the viewer to see foot passengers promenading in the tunnel. The arches help to indicate perspective. It was probably sold as a souvenir. Even before completion of the tunnel, the canny businessman Brunel allowed visitors to tour the works, at the cost of one shilling.
Wikipedia : Thames Tunnel