Usually when I think of Hong Kong I think of this type of view:
But of course the entire place can't be skyscrapers, as shown on this stamp of Po Pin Chau sea stack, located in Hong Kong's Global Geopark. Click this link to wikipedia for more information. The rocks are examples of hexagonal columnar jointing. The stamp is from the series of definitives issued in 2014.
For more postage related to rocks and geology, explore the links at Sunday Stamps.