also: たて
mansion; manor house; official residence
Only with reading たち
Poetic or literary term for a noble's mansion or an official residence. Especially read as たち.
その貴族は広大な館に住んでいた。
The noble lived in a vast mansion.
small castle; fort
Only with reading たて
Poetic or literary term for a small castle or fort. Especially read as たて.
山の上に小さな館が築かれた。
A small fort was built on the mountain.
The lord's mansion stood on top of the hill.
彼はこの地に館を構えていた。
He had a mansion built for himself in this area.
城 is the everyday word for a castle, while 館（たて）is a poetic, literary term for a smaller fort or stronghold.
Standard kanji spelling for both readings; context determines which reading is intended.
Kana spelling for the たて reading, used when the kanji might be misread as たち or やかた.
The kanji 館 means 'building' or 'mansion'. The readings たち and たて are native Japanese readings (kun'yomi) with specialized historical meanings. The exact derivation of these readings is uncertain.