couldn't believe (your) eyes

if you say that you couldn't believe your eyes when you saw something, you mean that you were very surprised by it.

She couldn't believe her eyes when she saw him drive up in his new car.

I could hardly believe my eyes. They'd made so many changes, it looked like a completely different house.

• bear witness to
• bear witness to something
• be as American as apple pie
• be as bald as a coot
• be as black as are is painted
• be as black as it is painted
• be as black as you are is painted
• be as black as you it is painted
• be as blind as a bat
• be as bright as a button
• be as brown as a berry
• be as busy as a bee
• be as clean as a whistle
• be as clear as crystal
• be as clear as day
• be as clear as mud
• be as cold as ice
• be as cool as a cucumber
• be as crazy as they come
• be as [crazy/rich etc.] as they come
• be as cute as a button
• be as daft as a brush
• be as dead as a dodo
• be as dead as a doornail
• save your bacon