Hidden Roman treasures: Borromini's optical illusion.

Palazzo Spada, located between Campo de' Fiori and Rome's river Tiber, is home to a gallery whose sumptuous art collection contains works by 16th- and 17th-century masters such as Caravaggio, Guido Reni, Guercino, Titian, Baciccia, Dürer, Jan Brueghel the Elder and Rubens. However the palace is also home to one of Rome's hidden secrets: the optical illusion by Baroque genius Francesco Borromini. 

This stunning example of forced perspective – commissioned by Cardinal Spada in 1632 – is centred around a magnificent colonnade whose diminishing rows of columns and rising floor level trick the eye into thinking the corridor is 37 metres long instead of its actual nine-metre length. Borromini's spectacular trompe-l'œil effect is compounded by what appears to be a life-size statue at the end of the colonnata; the statue of Mars - the Roman god of war - is in fact only 60cm high.

The €5 entry fee to Galleria Spada includes a visit to Borromini's architectural masterpiece which is located in the arcaded internal courtyard on the ground floor of the palace. Palazzo Spada can be found in Piazza Capo di Ferro 13, not far from Campo de' Fiori.
Open Wed-Mon 08.30-19.30. Tues closed. Last entry 19.00. Open for free on first Sunday of every month. Guided tours in English and Italian available on prior booking, tel. 066832409. For details see website.