在 + 笼子 + 里
The noun 笼子 (lóngzi) means "cage," referring to an enclosure used to confine animals or, figuratively, people. It is often used with 里 to indicate being inside the cage. For example, 关在笼子里 means "locked in a cage."
那只小鸟被关在笼子里,看起来很可怜。
Nà zhī xiǎo niǎo bèi guān zài lóngzi lǐ, kàn qǐlái hěn kělián.
That little bird was locked in a cage and looked pitiful.
他打开笼子,让兔子自由地跑出去。
Tā dǎkāi lóngzi, ràng tùzi zìyóu de pǎo chūqù.
He opened the cage and let the rabbit run out freely.
笼子里的猫一直在叫,想要出来。
Lóngzi lǐ de māo yìzhí zài jiào, xiǎng yào chūlái.
The cat in the cage kept meowing, wanting to get out.