Why is 'paradise' a word for a walled garden, and what is a charbagh?

A charbagh, meaning "four gardens" in Persian, is a garden divided into four quarters, usually by channels of water that meet at a small square basin in the centre. The layout began in the paradise gardens of the Achaemenid Empire, and after the Muslim conquest of Persia it was considered to represent the four gardens of Paradise mentioned in the Quran, with the waterways standing for four rivers. The garden may also be divided by walkways instead of flowing water.

The word paradise itself comes from this tradition. An old Iranian word, pairidaēza, meant "walled-around", a walled garden. Greeks borrowed it as parádeisos, the Romans turned it into paradīsus, and it became our paradise. Cyrus the Younger was alleged to have told a Spartan commander that he gardened daily when he was not campaigning, and he called the park he laid out at Sardis his "paradise".

A garden like this was also practical. In Iran's dry heat, shade and water matter, and water could arrive through a qanat, a tunnel that carries water from an aquifer. But gardens were more than relaxation: they were also a way to show power, hold audiences and celebrate victories and marriages.

From Iran the pattern spread across West Asia, South Asia, North Africa and al-Andalus. Later the Mughal emperor Babur brought it to India, trying to recreate the cool air of his homeland. The most famous charbagh of all surrounds the Taj Mahal, where each of the four parts holds sixteen flower beds.