This is the 17227th most frequent Russian word.
строящимся
"Under construction."
In this sentence, "строящимся" is used as an adjective modifying "мостом" (the bridge), indicating that the bridge is currently being constructed.
Этот город славится строящимся мостом.
This city is famous for the bridge currently under construction.
Here, "строящимся" modifies "кварталом" (the district), describing the district as one being constructed.
Мы обсудили проект, связанный со строящимся кварталом.
We discussed the project related to the district under construction.
In this example, "строящемся" serves as a descriptor for the "культурном центре" (cultural center), emphasizing its ongoing construction state.