21.   Mexico City, founded on the site of the Aztec city of Tenochtitlan, was surrounded by lakes and an intricate system of dams and canals.

22.   They have developed an intricate monitoring system with scores of spy cameras and sensors to ensure that Iraq does not try to revive those programs.

23.   Tu described an intricate system used to smuggle the heroin in false car doors and hollowed-out truck floor boards.

24.   The intricate system was devised to keep the transaction with Boeing tax free.