A fortress-like edifice shoehorned into a narrow six-storey sliver, the Palau Güell was Gaudí’s first major commission, begun in 1886 for textile baron Eusebi Güell. After years of renovation, it reopened in 2011, and once again visitors can look around the subterranean stables, with their exotic canopy of stone palm fronds on the ceiling, and the vestibule with ornate mudéjar carved ceilings from which the Güells could snoop on their arriving guests through the jalousie trellis-work. At the heart of the house, the spectacular six-storey hall, complete with musicians’ galleries and topped by a dome, is covered in cobalt honeycomb tiles. It’s a somewhat gloomy place, but the antidote lies on its roof terrace, decorated with a rainbow forest of 20 mosaic-clad chimneys. The Palau Güell was declared a UNESCO World Heritage Site in 1984.