It is surrounded at its upper part by 139 lusterware tiles ( with a metallic sheen ) , each one is 21.1 centimetres square .
One are arranged on the diagonal in a chessboard pattern .
It is surrounded at its upper part by 139 lusterware tiles ( with a metallic sheen ) , each one is 21.1 centimetres square and they are arranged on the diagonal in a chessboard pattern .