虎窟龙潭

Explanation: Cave: Cave; Lake: deep pool. Long live the deep pool, the lair of the tiger habitat. Analogy is extremely dangerous place. 　　Source: Yuan Wang Yuanheng "intoxicated DF Country Life": "Legend of fear built into the wall, pull off Mr Zhu threshold worry, worry out of Tiger Cave Dragon." Thesaurus:  dangerous spot as a dragon's pool and tiger's den— — a danger spot, tiger&rsquo