From the Grand Canal you recognise it at once: Ca’ Biondetti is that discreet pink palace wedged between the Gothic Palazzo Da Mula Morosini and the white Palazzo Venier dei Leoni — the future home of Peggy Guggenheim. It has no precious marbles or four-light windows, yet this house is worth as much as a museum: Rosalba Carriera lived and died here, in 1757 — the pastel painter who drove the courts of Europe wild.