天(tian)(tian)門洞是世(shi)界海(hai)拔(ba)最高的天(tian)(tian)然穿(chuan)山(shan)溶洞,三國吳永安六年(公元263年),嵩梁山(shan)峭壁(bi)轟然洞開,玄(xuan)朗(lang)如門,吳王(wang)視為吉(ji)祥(xiang),亦由此改稱天(tian)(tian)門山(shan),下置天(tian)(tian)門郡(jun)。天(tian)(tian)門洞南(nan)北對穿(chuan),門高131.5米,寬57米,深60米,拔(ba)地(di)依天(tian)(tian),宛(wan)若一(yi)道通天(tian)(tian)的門戶。
天(tian)門山(shan)(shan)海拔1518.6米,山(shan)(shan)頂面積2平(ping)方公里(li)。主峰東面絕(jue)壁(bi)有一巨(ju)型溶洞(dong),南北貫通(tong)透明如門,謂之——天(tian)門洞(dong),天(tian)門山(shan)(shan)由此而得名。天(tian)門山(shan)(shan)東嶺筆架山(shan)(shan),西扼七星山(shan)(shan)。十六峰環列左右,綿延(yan)數十里(li),如一道天(tian)然屏障。
天(tian)(tian)門奇景,古人有贊:永(yong)定勝狀,在天(tian)(tian)門山一山。故今人稱天(tian)(tian)門山為武陵之魂(hun)。天(tian)(tian)門山下,有澧(li)水發育(yu),切(qie)開山下谷地,使高山與谷地拉開極大高差,10公(gong)里之內,差高1300多米,造就天(tian)(tian)門山孤峰高聳、臨空獨尊(zun)的雄偉氣勢(shi)。