On the face of it, a special exhibition of Old Dutch Masters from a single private collection might sound like a severe case of coals to Newcastle. But visitors discouraged by the unmoving queues at the Rijksmuseum this spring are begging to differ. Just head over to H’Art (formerly the largest satellite of the State Hermitage Museum, St. Petersburg, rebranded in 2023), where you’ll find a thematically organized, painstakingly curated wealth of 18 Rembrandts, the only Vermeer in private hands, and major entries by Frans Hals, Jan Steen, and Jan Lievens, some 75 works in all. The source of these riches is the Leiden Collection, a “lending library” of art founded in 2003 by the Franco-American businessman Thomas S. Kaplan and his wife Daphne Recanati Kaplan. Over just two decades, the Kaplans have assembled a staggering 250 prime Dutch Old Masters, and what a treat it is to see the best of their best. Committed likewise to endangered-species preservations (big cats, snakes), the Kaplans seem shy of slapping their brand on all they touch. Their “Leiden” collection commemorates Rembrandt’s birthplace, while the current show celebrates Amsterdam’s Golden Age on the occasion of the city’s 750th birthday. —Matthew Gurewitsch