and since this discovery more than 120 miles of passageways have been mapped. 自从那次发现之后 迄今已测绘了120多英里的地道
but cave explorers were soon to make an even more astonishing discovery. 但是洞穴探险家们 很快又有了更惊人的发现
There is, in fact, more life here than anyone would think possible, 事实上 这里的生物数量 远比人们预料的更多
but the biggest surprise is something altogether more bizarre. 不过更大的惊奇莫过于 那些更奇怪的东西
When the nearest exit may be hundreds of metres or more away, 最近的出口可能远在 几百米之外或者更远的地方
So far, more than 350 miles of underwater galleries in the Yucatan have been mapped, 人们迄今为止已绘制了350英里的 尤卡坦半岛地下水系图
as each year rainwater eats away a little more limestone. 因为每年雨水都会侵蚀掉少许石灰岩
often more than 60 metres from the floor. 通常高出地面60多米
It takes more than 30 days to complete one. 每个燕窝得花上30多天才能完工