London - Old Royal Observatory

The Royal Observatory, founded in 1675 by Charles II to promote safer navigation, was housed until 1967 in Flamstead House, designed for the purpose by Sir Christopher Wren. The Observatory was moved to Herstmonceux in Sussex and subsequently to Cambridge in 1990. Flamstead House contains a collection of old astronomical instruments, including Harrison's Original Chronometer. Four of the rooms are furnished in the style of the 17th century. On a mast topping one of the towers of the house is a red time ball which drops from the top of the pole at 1 pm precisely every day - a device originally intended to enable vessels in the river to regulate their chronometers.

The zero meridian of longitude, dividing the globe into