Close to the grottos, there is a cinema inside a deserted railway tunnel. 洞穴的附近有一个废弃的铁路隧道，里面设有电影院。
It is shown that an electrified railway tunnel is an effective channel for transmission of language and slow digital signals. 研究表明，电气化铁路隧道是语音和低速数字信号传输的有效信道。
