Royal Observatory

Drawing over 1.5 million people a year, the Royal Observatory is one of several historic attractions that make up the UNESCO World Heritage Site known as Maritime Greenwich. Most of them go to see and straddle the Meridian Line, 0º Longitude, which since 1884 has been the starting point for measuring time and distance around the world. In fact, there is a great deal more to enjoy here - not least the terrific views north from the hill in Greenwich Park where the world's first purpose-made scientific building was constructed in 1675 by order of King Charles II. There is a planetarium, an Astronomy Centre devoted to unravelling the mysteries of the universe, and - my favourite section - the Time Galleries where you can admire the ingenious timepieces and instruments constructed in the 18th century to solve the great problem of how to measure longitude.