Tilework, Park Güell | Photo: Constanze Wutke
One of the techniques Gaudí employed in his amazing work was trencadis tilework mosaics (aka pique assiette). Trencadis (from the Catalan trencar, to break) involved using broken tile shards to create the mosiacs.
Perhaps the best known example is on the dragon guarding the gate to the Park Güell, where it is also to be found on the sea-serpent bench that runs round the esplanade at the top (detail shown in the picuture, above)
Popular legend has it that Gaudí used a naked lady's buttocks to get the mould for the bench just right!