One of the lesser-known sights in Hong Kong is shown in this picture, which I lifted from http://www.1oclockgun.org.uk/hongkong.html because the photos I took are at home.

This is a time ball.Back in the days before GPS, it was vital for ships to have an accurate clock on board if they were to know where they were. This time ball was used in the late 19th-early 20th century by the ships in the harbour to set their chronometers. Normally, the ball was raised up to the top of the pole on the roof of the building. Every day, the Hong Kong observatory would do observations of the sun to determine the local time exactly. They would send a signal to the operator of the time ball, and at precisely 1:00 p.m., the ball would drop from the top to the bottom of the pole. The ships would set their clocks accordingly.