The impressive architecture of Angkor Wat conveys a sense of harmonious design, but recent survey using ground-penetrating radar (GPR), coupled with targeted excavation, reveals a more complex picture. Fragmentary traces of a quincunx of earlier towers have been detected, which were partially demolished when the outer enclosure and western gateway were completed. Are these the remains of a shrine used during the construction period? If so, they throw new light on associated ritual activity during the building of Angkor Wat.