大厦 dàshà mansion

(used in the names of grand buildings such as 百老汇大厦 Broadway Mansions (in Shanghai) or 帝国大厦 Empire State Building etc)

怎么记住“大厦”: 大 big + 厦 large building = mansion.

汉字

大厦 (dàshà) means a large, often grand building - typically an office tower, hotel, or landmark structure.
Frequently appears as part of proper names: 帝国大厦 (Dìguó Dàshà, Empire State Building), 广播大厦 (Broadcasting Mansion).
Compare with 大楼 (dàlóu), a more neutral word for a large building (office building, apartment tower) - 大厦 carries a grander, more impressive connotation, often used for named landmark buildings.
Not used for small or ordinary buildings - reserve it for tall, prominent structures.