a large metal cannon sitting in front of tall buildings

This is the bow of a 'ship' on the land! The 'ship', The Whampoa'(黃埔號), is actually a shopping mall in a private residential estate called Whampoa Garden. This place was originally a ship building dockyard. Land reclamation had turned this area into a low rise residential area. The property developer built such a shopping mall in the shape of a ship to create an iconic landmark. This cannon, made in 1872, was a British naval cannon discovered here. Whampoa Garden is named after the historical and renowned Chinese modern naval academy, which was also called Whampoa in Guangdong province in China.