本館
ほんかん · honkan · JLPT N1 · noun
construction
🏢 本 (main, origin) + 館 (building, hall) = main building
本 also means book or origin. 館 is a hall or large building, as in 図書館 (library), so 本館 is the main hall of a campus or complex.
本 — tree 木 + mark at base
本 is a pictograph of a tree (木) with a stroke at its base, marking the roots. From this 'root' meaning it extended to 'origin,' 'source,' and 'foundation.' In modern usage it also serves as a measure word for bound objects like books.