I can't say if a conjuction should be used between A and B, but generally speaking the less commas or conjuctions you have, the smoother the sentence. Grammatically, the sentence has a few issues (I wouldn't correct them here because it isn't the main point of your question). However, from a readability point of view, it looks just fine without any conjunctions.

That's great. I get it. Thanks a lot

In my opinion, the word 'however' should join the two as such; Obviously, the city of xi’an is my priority. We all know that xi’an is the capital of shanxi province in china. However what really impressed me the most is that in regard to one of oldest cities in china, xi’an is the oldest of the four great ancient capitals. Also add the word 'the' in front of 'most in the second section as it allows the sentence to flow more easily. Also, try to avoid using the word 'queer' the way you did at the end. Another word such as 'strange' or 'odd' would be more suited to what you're saying. In some, and I'm sure most, English speaking cultures the word 'queer' heavily refers to homosexual people. In today's society anyway. Also remember to use capitals for names! (China, Xi'an).