National Museum in Warsaw

Most national museums grow from royal collections. Warsaw's, founded in 1862, has as its strangest treasure a set of wall paintings that were dug out of the Nubian desert barely in time. In the 1960s the Aswan High Dam was about to flood a long stretch of the Nile in Sudan, and a Polish team led by the archaeologist Kazimierz Michałowski excavated the buried cathedral of Faras. Under the sand they found scores of medieval Christian frescoes, and by agreement with Sudan a large share came to Warsaw.

The Faras Gallery now shows these serene, wide-eyed bishops and saints in a darkened hall, the only collection of its kind in Europe and a whole lost Christian kingdom brought back into the light.

The museum holds much more, from Polish painting to ancient art, including Jan Matejko's Battle of Grunwald, a vast and crowded canvas of a 1410 victory over the Teutonic Knights that the Germans put a bounty on during the Second World War. Staff hid it, and it survived rolled up in secret, one of many things in this building that came close to being lost.