The Palazzo Pitti in Florence was built on the south bank of the River Arno by Luca Pitti in demonstation of his rivalry with the Medici. Unlike the Palazzi in the city centre it is freestanding and backed by the Boboli Gardens. Work on the central block, originally designed by Brunelleschi, was commenced in 1447 after his death and continued by Luca Francelli. The building is heavily rusticated, the degree of rustication decreasing in each of its three storeys. Incomplete on the death of Luca Pitti in 1472, the building was worked on by Bartolemeo Ammannati from 1560. He converted the two ground floor side doors of the original central facade to windows, these being replicated by Giulio and Alfonso Parigi the Younger when the building was extended from 1616. The building's outer projecting wings were added from 1764-1783 by Giuseppe Ruggieri. The building now houses museums containing the art collections of the ducal rulers of Florence and Tuscany after being the ducal residence from the mid-sixteenth century to the early twentieth centuries. Ruskin praised the 'noble beauty' of the building's rustication when discussing 'typical beauty' in Modern Painters II (1846) ( Works, 4.137) and again in 'The Lamp of Power' ( Works, 8.115). In Val d' Arno he was less complimentary when comparing Renaissance palazzi with Romanesque domestic buildings ( Works, 23.83) and again in The Æsthetic and Mathematic Schools of Art in Florence ( Works, 23.243).