Charlotte Mullins comments on The interior of the Temple of Neptune, Paestum

THIS architectural drawing was one of 9,000 completed by the neo-classical architect John Soane and his office. It was completed in 1806 and shows the Temple of Neptune, a recently rediscovered Doric temple dating from about 450BC in the town of Paestum, Italy. Paestum was a Greek colonial settlement near Pompeii dedicated to Poseidon. When the temple was brought to the attention of Grand Tour travellers by Giovanni Battista Piranesi’s etchings in 1778, it was dubbed the Temple of Neptune, the Roman equivalent of Poseidon, but it has subsequently been attributed to Hera (an altar to Zeus has also been found there).

Piranesi created a series of imposing black-chalk drawings of the three Doric temples still standing in Paestum in 1777. He died before he could fully translate his series to etchings, so his son finished them and published them posthumously in 1778.

Soane’s version of the Temple of Neptune is more orderly and informative than Piranesi’s. It shows collapsed columns in the foreground and a sharp perspective through the roofless travertine temple to the rear pediment. Grand Tourists mill around the fallen pieces and emphasise the scale of the temple, which was 200ft long.

Soane met Piranesi in Rome shortly before the artist’s death. The architect later acquired his Paestum drawings and they can be seen today in the Sir John Soane’s Museum in London, together with Soane’s vast collection of 30,000 architectural and topographical drawings. This sketch is featured in the exhibition ‘Hidden Masterpieces’, until June 5.