寺 (sì) means "temple" and typically refers to a Buddhist temple. It often appears as part of compound place names, such as 山寺 (mountain temple). Many famous Chinese landmarks include 寺 in their names, like 少林寺 (Shaolin Temple).
山上有一座古老的寺,香火很旺。
Shān shàng yǒu yī zuò gǔlǎo de sì, xiānghuǒ hěn wàng.
There is an ancient temple on the mountain, and it has a thriving incense offering.
我们去少林寺参观了一整天。
Wǒmen qù Shàolín Sì cānguānle yī zhěng tiān.
We visited the Shaolin Temple for a whole day.
那座寺里住着几十位僧人。
Nà zuò sì lǐ zhùzhe jǐshí wèi sēngrén.
Several dozen monks live in that temple.