What coverings were used to decorate the intricate design of the Gateway pool?

A Porcelain bricks
B Glass lenses
C Ceramic tiles

Each ceramic tile is a one-of-a-kind, hand-painted piece made using traditional methods of craftsmanship. The tiles were designed specifically for the artwork and its location by Viúva Lamego, a Portuguese factory-studio and by Atelier Joana Vasconcelos.

The correct answer is Ceramic tiles.