《水经注·卷十九》
水渠南岸有汉时原来祭天的圆丘，成帝建始二年前，废除了雍五峙，才开始在长安南郊祭祀皇天上帝。应肋说：天郊在长安南面，就是这个圆丘。旧渠北有白亭、博望苑，是汉武帝为太子而建的，依他的爱好，让他在那里可与宾客交游。
即此也。故渠之北，有白亭、博望苑，汉武帝为太子立，使通宾客，从所好也。
On the southern bank of the channel, there is the original circular mound for the imperial worship of heaven. Before the second year of Emperor Cheng's Jianshi period, the imperial worship of the five mountains was abolished, so the ritual of worshipping the Imperial Heaven God was moved to the southern suburbs of Chang'an. Yin Lie said: Tianjiao was south of Chang'an, which was this circular mound. To the north of the old channel there was a white platform and the Boyang Garden, which was built by Emperor Wu of Han for his crown prince. The platform and the garden were built according to his preferences so that he could meet his guests there.