Memory techniques are far older than modern study tips. The loci method, or memory palace, dates back to the ancient Greeks and works by attaching items to familiar places you can mentally walk through. The story goes that the poet Simonides identified the victims of a collapsed banquet hall by recalling where each guest had been seated. Medieval and early modern writers built on the idea with imagined rooms, symbolic images and visual alphabets, and the peg system attached items to a fixed sequence of triggers. Acrostics, such as the rhyme for the order of the planets or the phrase Richard Of York Gave Battle In Vain for the rainbow colours, remain a common classroom tool.

Israeli reports also say the cabinet directed the military to prepare for a possible new attack on Iran.

Angkor, near Siem Reap in northern Cambodia, was the capital of the Khmer Empire, which ruled much of mainland Southeast Asia between roughly the 9th and 15th centuries. At its height the city spread across about 3,000 square kilometres, making it the largest pre-industrial city on Earth by area. Its growth depended on water: huge reservoirs called barays, along with canals and embankments, stored monsoon rain and carried it to rice fields. That system let farmers harvest more than once a year and fed a very large population through the dry season. The temple complex of Angkor Wat, built in the early 12th century, is the best-known monument and still stands at the heart of the park.