Question

There is also a 50-metre-long swiming pool 同义句

Answer 1

首先，楼主你的swimming打错了，要双写m的。
以下是答案：
1.There is also a swimming pool ,which is 50-metre-long .
2.There is also a swmming pool whose(of which) length is 50 meters.
这2个句子都是定语从句，第一个是非限制性定语从句，起补充说明的作用，去掉后面这个从句前面的句子依旧成立；第二个是限制性的定语从句，起先行词限制作用。
希望我的回答能帮到你

Answer 2

There is also a swimming pool, which is 50 meters long.

Answer 3

f鐧惧害鍦板浘

本数据来源于百度地图，最终结果以百度地图最新数据为准。