Sheikh Safi al-Din Khānegāh and Shrine Ensemble (1345, Iran)
It looks like 1960s op art, but this was made 600 years earlier for the Tughluq Temur Mausoleum in Huocheng, China. The arabic word Allah has been written four times in one symbol, and then tessellated.
Ceramic tile pavement design from Higham Ferreers, Northamptonshire, produced in 1340. Via