China is a vast country.  Beijing is the capital city and  is  the second largest city after Shanghai. Tiananmen Square, Forbidden City, Summer Palace, Bird’s Nest were very interesting. A visit to Great Wall of China is astonishing. It was  an emotional  feeling to climb the Wall. The high speed non stop train from Beijing to Shanghai was worth it.  
Shanghai is an energetic international metro-polis.   400 + Km/h speed Shanghai Maglev Train from the city to  airport was really breathtaking.
Hong Kong is a very busy city. Buy a 3 day tourist pass for airport express and MTR and you can reach to any corner of the  country very economically. Malls, Hotels and other business centers  built with underground MTR stations was really amazing. One day tour to Macau to have  a look at the lifestyle of the locals and visit  to Casinos was significant