Van Nelle Fabriek
Designed and built between 1925 and 1931, this modernist World Heritage–listed factory northwest of the city centre is an icon of 20th-century industrial architecture. Often described as a 'glass palace' (it's largely constructed of steel and glass), it functioned as a state-of-the-art coffee, tea and tobacco factory until the 1990s and now houses creative industries. Though closed to the public, the factory sometimes offers guided tours on weekends at 1pm (adult/child under 13 years €8.50/5); check the factory website for details. Urban Guides also runs one-hour guided tours (€15 per person) at noon on most Saturdays and Sundays (book ahead).
Sint Janskerk
Impressive for both its size and its magnificent stained-glass windows, Sint Janskerk had chequered beginnings: previous incarnations of the building burned down with ungodly regularity every 100 years or so from 1361 until the mid-16th century, when the current structure was completed. At 123m it is the longest church in the country. A free audioguide in English gives loads of information about the 72 windows, which together form the largest cache of in-situ 16th-century stained glass in the world.