Sotheby's will offer a large Venetian view of the Rialto Bridge painted by Francesco Guardi valued at around 20 million pounds ($30 million).
The auctioneer called the work "one of the greatest masterpieces of Venetian view painting ever executed." It will go under the hammer in London on July 6.
It is one of four works painted by Guardi on such a grand scale, all executed at around the same time in the late 1760s.
