underground

The city has a well-developed underground transportation system.

这座城市有一个非常发达的地下交通系统。

They explored the underground caves and found many interesting formations.

他们探索了地下洞穴，发现了许多有趣的结构。

The underground passage was dark and damp.

地下通道又黑又潮湿。

Some animals live in the underground burrows.

一些动物生活在地下洞穴中。

The treasure was hidden in an underground chamber.

宝藏藏在一个地下密室里。

The underground river flowed quietly through the cave.

地下河流静静地在洞穴中流淌。

He works in the underground mine and earns a decent living.

他在地下矿井工作，收入还不错。

The underground parking lot is always full during peak hours.

地下停车场在高峰时段总是满的。

They held an underground concert in a secret location.

他们在一个秘密地点举办了一场地下音乐会。

The underground resistance movement fought against the invaders.

地下抵抗运动与侵略者进行斗争。