稳如泰山
Meaning
Rock solid; utterly stable and unmovable.
In a sentence
The old bridge is 稳如泰山 after the repairs.
Usage note
Mount Tai is a real mountain in Shandong, used as the image of stability.
Where you see it in Brain Challenge
This idiom appears in the picture-idiom levels as a picture or number clue. When the clue shows numbers, the digits usually become the first characters of each half of the idiom — that is why so many chengyu start with 一, 三, 五, 七, 九 or 十.