Main Building
noun
One of the meanings of 本 is main (which is what we're using here). The main public building is the main building.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
本館には、ようじ教室の部屋がへいせつされています。
The main building has a classroom for pre-school children.
本館のれきしをゼロから教える本を作ります。
We are going to make a book that teaches the history of the main building from scratch.
あの百貨店の本館で働いている店員は、別館で働いている人たちに比べて、なんか働かされてるって感じだった。愛想がやけに悪いっていうかさ。
Lots of the people working in the main building of the department store act like someone is forcing them to work, compared to those working at the annex. They have awfully bad attitudes.