The author recalls the history of those paintings of Bernard Belotto, known as Canaletto, which represent the Warsaw landscapes. They were painted for the Royal Castle of Warsaw during the period of 1767=—1780. In 1832 they were taken to Moscow and Petersburg and they underwent restoration there. They were taken back again in 1922 but the full conservation works were carried out not before than during the period of 1973—1975 at the request of the National Museum of Warsaw. The restoration consisted of the removing of the old lining, sticking of the new one, removing of the dimmed varnish, filling with mastiks, varnishing and stippling. In the course of conservation works, on the back of the original paintings there were found the numbers of the Royal Gallery catalogue and also serial numbers indicating arrangement of the pictures in Canaletto’s Room of the Royal Castle which will make the reconstruction of the Royal Castle’s interiors much easier. There were also found the signs of patching up the pictures which were made in the twenties years of the 20th century. It should be added, moreover, that in the course of works connected with post-war reconstruction of the oldest parts of Warsaw, the pictures (painted (by Canaletto and representing the sights of Warsaw proved to foe the priceless historical and iconographie material.