treasury; treasure house; storehouse; repository
treasure trove; rich source (of)
図書館は知識の宝庫だ。
A library is a treasure house of knowledge.
この地域は海産物の宝庫として知られる。
This region is known as a treasure trove of seafood.
あの博物館は民族資料の宝庫で一日いても飽きない。
That museum is a treasure trove of ethnic materials, and you could spend a whole day there without getting bored.