The big square is placed directly above the colonnade and limited on the city side by the famous undulating bench. This bench is a marvel of shape, color and contrasts.
To develop that work, Gaudí was assisted by the architect Josep María Jujol, a specialist in the design of "trencadis" (decoration with broken ceramic). That bench looks like a giant collage.
Unfortunately some parts of the bench were destroyed because vandalism and are now substituted by white ceramics, after a conscientious reformation, but...better to speak about is to see it!.
 

Different views of the undulating bench:

The back rest of bench show a big design fantasy:

Variety of designs on frontal side of bench:

  To:  Main gateway
         Big square and Colonnade
         Gaudí house
         Paths and viaducts