四通八达
Meaning
Well connected in all directions — said of roads, transport networks, or a well-placed location.
In a sentence
The new station is 四通八达, with lines to every district.
Usage note
Almost always about physical connectivity, not social networks.
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.