大樓正在建造。

The building is under construction.

Source: Tatoeba

Sentence Composition

1 大樓 dàlóu building (a relatively large, multistory one)

classifiers: 幢, 座
2 正在 zhèngzài to be in the process of (doing sth); to be currently ...-ing
3 建造 jiànzào to construct; to build