No smoking on the street
Unlike in mainland China, the world's largest consumer of tobacco, it is rare to see people smoking in Hong Kong, because it's illegal to smoke in the vast majority of public places. You may come across some streets with non-smoking signs, and more commonly it's forbidden in parks, on beaches and in other areas designated for relaxation, where even taking pets is prohibited.
For those who haven't already witnessed construction work in certain Asian cities, this is another surprising detail. Buildings are constructed with their help of bamboo scaffolding tied together ropes, even some skyscrapers!
Speaking of skyscrapers...
Hong Kong has the most skyscrapers - buildings with more than 14 floors - in the world, doubling that of the second-place city, New York!
The name Hong Kong translates as "fragrant harbour", a possible reference to the sweet taste of the harbour water from the Pearl River, or to the smell from the incense factories lining the coast of northern Kowloon (whose name literally means "Nine Dragons"!).