The Museu Nacional de la Ciència i de la Tècnica de Catalunya — mNACTEC for short — fills a colossal early-20th-century textile mill on the south-west edge of central Terrassa. The mill itself is the star exhibit: the great vaulted hall, with its 161 brick catenary arches and natural-lit sawtooth roof, is one of the great industrial spaces in Europe.
The permanent collection traces the technological transformation of Catalonia from the early industrial revolution to the present: weaving machines, locomotives, early aircraft, radios and televisions, the country's first electrical generators, a working steam engine. Special exhibitions are usually thoughtful and well-presented. Allow at least two hours, longer if you have an interest in industrial history. The cafe is excellent. Closed Mondays.