first known railway print. Following a failed bid to supply stone to buildings in London, Allen wanted a building which would show off the properties of Bath stone as a building material. Hitherto, the quarry masons had always hewn stone roughly, providing blocks of varying size. Wood required stone blocks to be cut with crisp clean edges for his distinctive classical façades. The stone was extracted by the "room and pillar" method, by which chambers were dug out, leaving pillars of stone to support the roof. Bath stone is an Oolitic limestone comprising granular fragments of calcium carbonate laid down during the Jurassic period (195 to 135 million years ago). An important feature of Bath stone is that it is a freestone, that is one that can be sawn or 'squared up' in any direction, unlike other rocks such as slate, which has distinct layers. It was extensively used in the Roman and Medieval periods on domestic, ecclesiastical and civil engineering projects such as bridges. John Wood, the Elder was commissioned by Ralph Allen to build on the hill overlooking Bath: "To see all Bath, and for all Bath to see". Wood was born in Bath and is known for designing many of the streets and buildings of the city, such as The Circus (1754–68), St John's Hospital, (1727–28), Queen Square (1728–36), the North (1740) and South Parades (1743–48), the Mineral Water Hospital (1738–42) and other notable houses, many of which are Grade I listed buildings. Queen Square was his first speculative development. Wood lived in a house on the square, which was described by Nikolaus Pevsner as "one of the finest Palladian compositions in England before 1730". The plan for Prior Park was to construct five buildings along three sides of a dodecagon matching the sweep of the head of the valley, with the main building flanked by elongated wings based on designs by Andrea Palladio. The plans were influenced by drawings in Vitruvius Britannicus originally made by Colen Campbell for Wanstead House in Essex, which was yet to be built. The main block had 15 bays and each of the wings 17 bays. Between each wing and the main block was a Porte-cochère for coaches to stop under. In addition to the stone from the local quarries, material, including the grand staircase and plasterwork, from the demolished Hunstrete House were used in the construction. Construction work began in