Crickhowell Bridge will close for three consecutive nights next week in order for emergency work to be carried out.
The A4077 road, which crosses the bridge, will be closed on Friday, Saturday and Sunday (July 21, 22 and 23) from 8pm to 6am.
The closure is on behalf of Powys County Council, while they do emergency protection works on the bridge.
The bridge, which spans the River Usk, connects the communities of Crickhowell and Llangattock.
The official diversion for the journey is via Abergavenny.