UNDERSTANDING XUAN KONG玄空
The word XuanKong 玄空had been translated and interpreted in many ways. Mostly it depends on the Fengshui school’s understanding of this word.
The SanYuan 三元（Fengshui school）understanding and interpretation is slightly different from that of the SanHe 三合 （Fengshui school）understanding.
In the QingNang AoYu 青囊奥语and TianYu Jing天玉经, there were several mention of this word XuanKong玄空.
To quote the classic QingNang AoYu：
雌与雄交会合玄空，雄与雌玄空卦内寻
Ci and Xiong interaction conforms to XuanKong,
Xiong雄 and Ci雌 can find within the Gua of XuanKong玄空.
Rocky mountians have bad qi
Rocky montain
Rugged mountains and riverbeds.