A giant view of Venice by Canaletto is expected to fetch £5m when the art collection of a financier and entrepreneur comes up for auction this summer.
Antonio Champalimaud's collection of works by artists including Fragonard and Boucher, French furniture, sculpture and Chinese porcelain has an estimate of £15m. Most of the proceeds will go to a medical foundation Mr Champalimaud set up for his home nation, Portugal.
Having made sure his seven children were all financially secure before he died last year at the age of 86, he established his foundation with an initial bequest of €600m (£420m).
Canaletto's The Bucintoro at the Molo on Ascension Day captures the scene at the Molo, near St Mark's Square, with the Doge's state barge, the bucintoro, moored by his palace, as crowds celebrate the city's great feast day.
The painting, part of the most ambitious series of decorative canvases of the artist's career, was commissioned by an Englishman, Peter King later the 5th Lord King, in the mid-18th century. A pair of smaller Canalettos, of the Piazzetta and Piazza San Marco, are also on sale at up to £1m for the pair.
The collection highlights will be on show at Christie's in King Street, London, from the start of June.