These examples of Spanish 20th-century avant-garde art blend in so well with their surrounding urban landscape that most people walk past them without noticing. It's worth taking the time to stop and look though, and it's free. You'll see 15 sculptures by artists as famous as Chillida, Subirachs, Torner, Alfaro, Chirino and Miró. Manoeuvering Chillida's piece, Sirena varada (Stranded Siren), into place was a feat of engineering in itself.