This roughly turn-of-the-century architectural style can be thought of as Art Nouveau as interpreted by Catalan Nationalism. Catalonia had been held down by previous central (Castilian) regimes, but in the 19th century was the first region of Spain to industrialize, and rapidly grow richer, and more culturally confident. This led to the Renaixença, with an emphasis on Catalan language, traditions, and creativity. The "New Art" of modern Europe was an inspiration to launch off in new directions, albeit ones which incorporated traditional motifs such as ceramics. And all this created the conditions in which a very individual genius like Gaudí could receive sponsorship and support. But while his is the best-known name, there were other talented and creative architects and artists as well.

Palau Güell

The first of Gaudí's major works, this townhouse was commissioned by Don Eusebio Güell in 1885, and cost was obviously no object. This is now a museum, and one can visit inside, unlike most of his other works, which are still private. Though only guided tours are permitted, with strange hours, and no pictures of the interior, it's well worth persevering.

Click on the small pictures to see larger ones.

The façade, relatively calm for Gaudí, though there's obviously something special happening up top!
Terrific wrought-iron work on the front.
Chimneys like popsicles! I like the bat on top of the tower surfaced with crushed rock.

Mansana de la Discòrdia: Casas Morera, Amattler, and Batllò

The "Block of Discord", with three very different houses from the three major Modernisme architects. First there is Domènech i Montaner's Casa Lleó Morera, then Puig i Cadafalch's Casa Amatller, and right next to it, Gaudí's extraordinary Casa Batllò
I came out of the Metro, looking from side to side to orient myself, then suddenly I caught sight of these houses. Woah! I'd seen pictures in books, but it's still amazing to grasp that buildings this weird really exist...
Casa Morera, from 1902, in a rather baroque floral style.
The full corner view.
Casa Amatller, from 1900, built for a chocolate manufacturer still in business. (And one can purchase reprints of contemporary Mucha, etc. posters.) A Flemish-looking gable.
On the doorway, St. George and the dragon, a common theme. I like the bold way the sculpture overflows the structure.
Inside the vestibule. Though one can't see it in these pictures, some of the little stone creatures holding up the stairway are engaged in various chocolate-making activities!
And finally the Casa Batllò, remodelled by Gaudí in 1907. The roof has always reminded me of fish-scales, or perhaps a dragon's back. 
The left-hand picture is a vertical panorama built from three horizontal images, warped to fit together smoothly. The night-time picture below has been heavily manipulated, just for fun; as the original was hand-held and rather shaky.

Casa Milà, or La Pedrara

This apartment building, built between 1906 to 1912, is known as La Pedrara, or the "rock pile" or "quarry". It's Gaudí's last major secular commission before he devoted his full energies to La Sagrada Família. It's been restored by the Caixa Catalunya Foundation, to the tune of about $20 million. One apartment is open for visits, and is a rare example of a complete Art Nouveau interior. 

It must have been tricky to build; plans in the attic musuem show that the interior structure is as non-orthogonal as the exterior, with an organic-looking cellular organization. But Gaudí must have been a very competent engineer as well as a supremely creative designer, for his unusual structures all seem robust and lasting.
Some details: a doorway, an exterior door-handle, and furniture inside one of the apartments.
More weird and wonderful chimneys...

Hospital de la Santa Creu i de Sant Pau

This complex, started by Domènech i Montaner in 1902, and worked on through his retirement in 1912, is still a working hospital. It was finally finished in 1930, overseen by his son Pere. It's a cluster of cute little pavilions that are pleasant to amble around.

Parc Güell

Another commission for Don Eusebio Güell, the park was intended as the start of a private housing development. Gaudí worked on the park from 1900 to 1914, but in the end just two houses were built, and the park was opened to the public in 1922. The fabulous ceramic decoration is the work of Josep Maria Jujol, Gaudí's assistant on many projects.

The park is located outside of the center, on a hill with fine views over the city. It was meant to be a garden-suburb, a retreat from the city.

To either side are the entrance pavilions.
From the entrance gate to the lizard fountain, the latter now one of the icons of Barcelona.
The plaza, rather amazingly suspended over columns, with the superb undulating ceramic bench that surrounds it.
Under the hall of columns, a ceiling medallion.
The Casa Museu Gaudí, designed and built in 1904 by Francesc Berenguer. Gaudí lived here until he moved to the Sagrada Familia site for the rest of his life. It's now a small museum, with a few pieces of furniture from various of his houses, etc.

In the Barri Gotìc; Els Quatre Gats and Palau de la Música Catalana

Two rather different buildings in the Medieval Quarter:

Els Quatre Gats, or the Casa Marti, is the famous hangout of Pere Romeu, Ramon Casa, Pablo Picasso and others. It was Puig i Cadafalch's first commission, built in 1897 in a rather flamboyant new-Gothic style. Unfortunately I never made it in for a drink or a meal. 
On the left, just another nice doorway, but on the right, Domènech i Montaner's magnificent Palau de la Música Catalana of 1908. I didn't do it photographic justice at all, though the interior is particularly splendid (and no pictures allowed; see their web site for some glories). Note the multi-colored columns on the balcony, each different!

Finca Güell

This was a riding school and stables for the family of Don Eusebio Güell, completed in 1887, while Gaudí was working on the Palau Güell. It's not open to the public now, but is famous for its extraordinary dragon gate.

Casa de les Punxes, Casa Macaya, etc.

A final modernisme roundup:

Puig i Cadafalch's Casa Terrades of 1903, known as the Casa de les Punxes or "House of Spikes". 
An anonymous curvaceous façade on the Av. Diagonal.
Another by Puig i Cadafalch, the Casa Macaya of 1901. It's styled after the medieval/baroque mansions of the Barri Gotìc
Another anonymous and colorful façade, noticed by chance as I was exiting the bank branch below after changing some money.