expression, noun
gold mine; treasure trove; mountain of treasures
Idiomatic expression meaning a place or source of great wealth, valuable resources, or abundant opportunities. Can be used literally or figuratively.
この図書館は知識の宝の山だ。
This library is a treasure trove of knowledge.
彼のアイデアはビジネスの宝の山だった。
His ideas were a gold mine for the business.