A "concrete wall" refers to a physical barrier made of solid material called concrete. It is typically used to separate or enclose areas, providing privacy or preventing access. Full definition
Home brings to life the unheard voices of the young residents and staff who live and work behind the anonymous concrete walls of an inner city high - rise hostel. (tes.com)
Because it's set underground with concrete walls, it's energy - efficient. (cnbc.com)