London: The Royal Observatory in Greenwich, United Kingdom, is a historic and scientific monument visited by people from across the globe.

Commissioned in 1676 during the reign of King Charles II, the observatory is situated on a hill in Greenwich Park southeast of London and overlooking the River Thames to the north.

River Thames seen from above the observatory

The building's main observatory the Flamsteed House has the third oldest red-colored time ball and used to tell time.

The observatory is situated on a hill at Greenwich Park

In 1855, the first electric clock in the world was installed and with the device, the Greenwich was born.

Overview from the top of the observatory

Behind the Flamsteed House, a separate ward is built with a huge iron dome constructed in 1893. This facility housed once the largest telescope in the world designed by astronomer Sir Howard Grubb.

Flamsteed House has the third oldest red-colored time ball

Despite becoming less important in the field of astronomy, the Royal Observatory in Greenwich maintains its status as one of the most important historical and scientific monuments from the 18 and 19 centuries.