Palau Guell was Antoni Gaudi's first major commission, built between 1886 and 1890 for his patron Eusebi Guell. It's a UNESCO World Heritage Site and one of the best places to see Gaudi's early style before the organic forms of his later work took over.
The facade on Carrer Nou de la Rambla is restrained by Gaudi standards — wrought-iron parabolic arches mark the entrance — but inside, the building explodes with invention. The central hall rises through several floors to a parabolic dome perforated with small holes, creating a starfield effect when sunlight pours through. The basement stables with their mushroom-shaped columns hint at the structural experiments Gaudi would later perfect at Park Guell and the Sagrada Familia.
The rooftop is the highlight. Twenty chimneys are clad in fragments of ceramic, marble, and glass — a riot of colour and form that anticipates the trencadis technique Gaudi used everywhere afterwards. The views over the Raval neighbourhood are a bonus.
Visitor numbers are capped, so the experience is far less crowded than Casa Batllo or La Pedrera. It's just off La Rambla, an easy detour on any walk through the old city.