被 + Noun + 所 + 包围
包围 (bāowéi) is a verb meaning "to surround" or "to encircle." It is often used in the passive construction 被...所包围 to describe something being enclosed on all sides. For example, 被树木所包围 means "surrounded by trees."
这座小岛被大海包围着。
Zhè zuò xiǎo dǎo bèi dàhǎi bāowéi zhe.
This small island is surrounded by the sea.
警察已经包围了整栋大楼。
Jǐngchá yǐjīng bāowéi le zhěng dòng dàlóu.
The police have already surrounded the entire building.
孩子们把老师包围了,争着问问题。
Háizimen bǎ lǎoshī bāowéi le, zhēng zhe wèn wèntí.
The children surrounded the teacher, eagerly asking questions.