I am a graduand of The University of Hong Kong. HKU is the first British university in oriental Asia, and has been, though rankings of course fluctuate, the No 1 university in Asia-Pacific, topping universities such as National University of Singapore, Peking University, University of Tokyo, University of Sydney, University of Melbourne, and Australian National University. It is the most selective university in Hong Kong, and is one of the most selective globally, with only around a 11% acceptance rate. In the field of geography, it ranks No 25 world-wide in 2014, down from No 20 in 2013.
Among local universities, HKU has the highest portion of international students, though like other local universities, it does usually mean mainland Chinese students. The official medium of instruction is English but since Hong Kong is a predominantly Cantonese-speaking city, despite having been a British colonial until 1997 and has English remained as one of our official languages (the other being Cantonese and traditional Chinese characters), students do tend to interact with each other in Cantonese, and hall activities do tend to be conducted in Cantonese. Other student activities are usually in both languages, and HKU does have the highest English grades for its intake and graduates. Our vice-chancellor and president is a white British man, who was a Cambridge-educated dean of medicine and dentistry at University of Bristol.
HKU is a campus university. You may see many spots on the maps, but you are likely to never really go out of the main campus. It is the oldest university in Hong Kong with more than 140 years of history tracing back to its origin (housing the founder of modern China, Dr Sun Yat-Sen even, qualifying him as a doctor), and thus is the only university with beautiful historical (colonial) buildings. Do not expect Hong Kong to be anything like Europe however - we don't have much historical buildings in general. The oldest building HKU manages is the University Hall (Douglas Castle), a student residence located a little far from campus.
Its location is convenient, but at the moment does not have a railway station (it's coming). But it is rather close to Hong Kong's clubbing districts, ie LKF and Wan Chai. It is right next to the CBD of Hong Kong (the historical Victoria City, which is now Central, Sheung Wan, Wan Chai, Admiralty, and Causeway Bay), and is on the prestigious mid-level areas, leading all the way up to the world-famous Victoria Peak.
I have never taken courses in geography so I cannot possibly comment on that.
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Academically, do not expect much. I personally was very underwhelmed by my experience intellectually at the university - I have been to three universities, and am about to go to another one, and I can rank it like this:
University of Cambridge >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> University of Hong Kong >>>>>>>>>>>>>>>>>> University of Queensland
Regarding the students: Even though they all have got really good grades, most of them are pretty average intellectually, with some of them being also very arrogant. The worst people you will meet are people in the halls who either are just residents (people who feel they are superior to you because they have lived there longer than you do), or committee members (elected people who feel they are the rightful monarchs if not gods and goddesses of the university-maintained halls). The christians are generally borderline tolerable. But these people add up to a very small portion.
The worst thing about the university is its administration. They, even though many are not Chinese, are pretty rigid in general and most treat undergraduates like children. But your experience might be very different as you are not Chinese and not a regular student.
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Do ask me any question regarding the university and the city. To address some of your preferences: HKU is quite close to the sea. HK is very hot and humid (similar to Singapore). HK is very crowded (much more than Singapore for some reason). Local students don't generally drink so you'd either be with other international students a lot or westernised ones if you go out clubbing all the time. Whether the sights are 'great' or the culture is 'interesting' is very difficult to respond to because they are very subjective and personal.