大开眼界

dà kāi yǎn jiè

eye-opening

Character by character

大dà
greatly

开kāi
open

眼yǎn
eye

界jiè
horizon

这次去非洲旅行，让我大开眼界。

This trip to Africa was a real eye-opener.

Tone: positive (praise).

让我大开眼界 can also be wry, for something outrageous.

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