I have to say that of all the places that I have visited, this is one of the best that I have gone and really enjoy and marveled at this art-piece. It's so so Chinese yet so Muslim. what a mixture of art and religion ....
This mosque, i believe one of the earliest mosques in China was build in 724AD during Tang Dynasty and has a history of 1270yrs! Amazing right?
Anyway ,.... found an article which is well written and informative online .... just read from the article for info : http://archnet.org/library/sites/one-site.jsp?site_id=9146 ..... as follows :
Behind the prayer hall, and accessed by two circular "moon gates" on either side of the portico wall, is the fifth court with two small constructed hills used for the ceremonial viewing of the new moon.