Museo Patio Herreriano is Valladolid's strongest modern-art stop, set in part of the former San Benito monastery. The old stone shell and clean gallery spaces work well together, giving Spanish contemporary art from the 20th century onward a calm, uncluttered home.
It is a good counterweight to Valladolid's churches, plazas, and royal history. The collection is serious without being overwhelming, and temporary exhibitions often make the museum worth checking even if you have visited before. Allow time to look at the building as well as the art.