There are a few things iconic to the visual identity of Barcelona. Its skyline. Its parallel and perpendicular streets crossing the Diagonal in unusual angles. The broken-tile mosaics. The Art Nouveau flowers on many buildings. And also the local style of mosaic used to cover the floors of so many shops, bars, restaurants and apartments.
The mosaics of interiors in Barcelona are what calçada portuguesa is for the streets of Lisboa – you can keep looking down and always find beautiful things to see. These mosaics decorate lots of bars and bistros in Barcelona, and also in many apartments and palaces.
The hydraulic mosaics or cement tiles are made by hand, one at a time, using mineral pigments, cement, a mould, and a hydraulic press. These cement tiles are not fired – there is no glaze layer on the surface of the tile.
They derive their durability from the combination of finely dehydrated ground Portland cement layer and a coarser layer of sand and cement. The pigment layer is hydraulically pressed into the surface and becomes a part of the tile. 
The first references of cement floor tiles date back to 1857. At the Universal Expo in Paris of 1867, the Catalan company of Garret, Rivet & Co. presented, to the whole world, the new innovative floor, made out of tiles that did not require baking because its system was based upon the press.
The tiles have a significant decorative component and they are made using metal stencils with various sections filled in different colors. The designs are usually a combination of 2, 4 or 6 types of pieces, and the mosaic is handmade, piece by piece, out of different pastes, with water, marble powder and white cement, sand and their respective pigment.
The procedure starts with pouring the color pasta in a special mold – an iron form drawing the outline that the mosaic would have. Created one by one, the tiles have 3 layers. The top one, where the decoration is, made of Portland cement, marble sand and pigments. The second layer, also about 4 mm thick, is the intermediate one, cement and sand, and its function is to absorb the excess of water from the pigmented layer. The third layer, the base of the tile, is around 12 mm thick and is made of Portland cement, regular cement and sand. With high porosity, this layer is the one that is in contact with the floor, and is very easy to adhere. Then the mould with the completed pattern is placed in a hydraulic press for being compacted. Then, it is extracted, dried, immersed in water and then left for 28 days until concrete to completely hardens, in a chamber with high humidity.
Go see nice hydraulic mosaic at Laie Pau Claris, a library & café-restaurant right next to Passeig de Gracia in a typical building with beautiful floors covering the floor with intricate patterns. Also stop by Pinar Miró, the showroom is next to el Born Center and you can find unique handmade designs, at Virreina, the Image Centre of Barcelona, free to visit.
Rutes de Barcelona 