Also, many world class architects became famous from their work in Barcelona: from Antonio Gaudi to Zaha Hadid, it there is little doubt that Barcelona is clearly one of the most important cities for architecture.
If you are interested in architecture, you may have heard before that Barcelona is famous for its display of 'Modernism'. This descriptive is commonly used to reference the city's distinctive style of architecture. Antonio Gaudi’s work can be easily related to that style. In reality, Modernism was an art movement present not only in architecture, and it gained notoriety when the Catalan renaissance was taking place.
Barcelona was Catalonia’s capital, so it’s only natural that it was vital for the Modernism movement, and it was here that many distinctive Catalan characters such as politicians, writers, poets, architects and artists helped in lifting the then little known, traditional and rural Catalan culture to match the progressive natures of Europe's most developed countries.
Gaudi is probably one of Barcelona most famous architects, but it was Lluis Domenech i Montaner who really kicked started Modernism. Montaner was born in 1850, and was notorious for being a prominent politician and also director of the Barcelona School of Architecture. He is considered as one of Gaudi’s most influential teachers. He published an essay in 1878 called 'In Search of a National Architecture', in the art journal La Renaixença. Montaner’s essay is now considered a seminal text of the Modernisme movement and reflects the Catalans' need of creating an independent identity by using the beauty of architecture and other arts.
Along with Barcelona's other world class architects, such as Gaudi and Puig i Cadalfach, Domenech i Montaner focused his vision towards a style that would clearly reflect the Catalan culture, as well as give Barcelona an aesthetic unique not only in Spain, but the rest of the world. There is no doubt that they achieved this with extraordinary success, and nowadays Barcelona owes much of its world class fame to 'the look' which these important men helped develop.
Modernista architecture can be easily recognized by the use of the curve over the straight line, organic and botanical shapes and details, the use of rich and vivid ornamentation, bright colors, and most importantly a disregard of symmetry and a very wide use of symbolism.
If you visit anywhere in Catalonia, you will easily see traces from traditional Catalan rural life and Catalan mythology, as well as Arabic patterns and decorations all over the buildings. The overall effect is a very particular style of architecture which is very organic and very colorful.
However, it is sometimes absurdly over the top with details and ornament. There are many people that find Barcelona's architecture a little too exaggerated with the details and ornaments. However, many of those decorations and mind-boggling shapes certainly look great on camera. It's easy to understand why they are so popular with tourists.
More information about Barcelona here.