CAMBODIA: The monuments of Angkor Wat include thousands of sandstone blocks—but where did they come from? Researchers recently undertook a study of the quarries used by the builders and identified more than 50 of them, active in different phases, about 20 miles northeast of the site, at the foot of Mt. Kulen. The team also investigated a canal-river system visible in satellite images, which they believe was used to transport the blocks to the site efficiently. —Samir S. Patel