Number + 层 + 楼
楼 (lóu) means "building" or "floor/story" and refers to multi-story structures. It is used both as a standalone noun and in compounds like 大楼 (large building) or 楼上 (upstairs). It frequently appears with the measure word 层 to indicate floor numbers.
对面那栋楼是新建的办公楼。
Duìmiàn nà dòng lóu shì xīn jiàn de bàngōnglóu.
The building across the street is a newly built office building.
他在楼上等你呢,快上去吧。
Tā zài lóu shàng děng nǐ ne, kuài shàngqù ba.
He's waiting for you upstairs; hurry up and go.
这座大楼的设计非常现代。
Zhè zuò dàlóu de shèjì fēicháng xiàndài.
The design of this building is very modern.