The arched chambers on either side of the sally port are identical bomb shelters for the fort's soldiers. They were built immediately after the bombardment of 1814, when it became obvious that such places were needed. Fort McHenry was never shelled again, and the bombproofs were never used for their intended purpose. The underground rooms in and around the star fort were not dungeons, despite their iron gates and dark narrow entrances. Bombproofs and magazines were built to protect personnel and ammunition from enemy artillery fire. Their multilayered brick vaulting made the bombproof strong, and six air shafts along the right side provided ventilation.