“Tiepolo in Milan”

This lovely, melancholic exhibition centers on art that doesn’t exist: ceilings painted in 1730-31, by the rococo master Giambattista Tiepolo, in the Palazzo Archinto, which, like most of Milan’s historical buildings, was destroyed by Allied bombing during the Second World War. (Sandbags saved Leonardo’s “Last Supper,” but not the convent it was in.) Paintings, drawings, etchings, books, and photographs that relate to Tiepolo's frescoes on mythological themes, and to the munificent Archinto family, vivify glories of a former time. The gossamer grays of hauntingly beautiful photographs, from 1897, convey the tones of colors that are now only guessable. The commission was Tiepolo’s first outside his native Venice, but, on the evidence here, he was already fully mature, crowning architectural spaces with heavens of epic imagination. If, like many people, you find Tiepolo hard to appreciate, this intimately absorbing show may initiate you in the charms—heart, soul, inventiveness, staggering ambition—of his art. (Frick Collection; Through July 14.)