Waldmüller: Landscapes

A quietly brilliant one to catch before it closes: this is the first exhibition anywhere devoted solely to Waldmüller's landscapes, with the Belvedere in Vienna lending the bulk of the works. His Alpine views of the Salzkammergut have an almost photographic clarity — crisp light, saturated blue skies — that rewards a slow, close look rather than a quick walk-through.

Free to enter and a genuinely underrated addition to a Trafalgar Square afternoon, but it shuts on 20 September, so don't leave it too long.