RD Site No.4 was a council estate in Smethwick, Sandwell. The RD Site No.4 project, construction of which started in 1961, consisted of two 20-storey towers; Croxhall Tower and Mill Tower. These have since been demolished. It was approved by Smethwick County Borough Council and maintained by Warley County Borough Council.
In April 1993, Croxhall Tower and Mill Tower were demolished in a controlled explosion by Doyle Demolition.