Immediately north of the Red Fort stands the Salimgarh Fort. It was built a century earlier than Red Fort. Its site is now bisected by railway which crosses the Ring Road by a bridge.
Islam, the son of Sher Shah Suri, built this island fortress between 1545 and 1554 to defend his father's city of Shergarh, located further south, against the projected return of Humayun. It, therefore, predates the Red Ford and Shahjahanbad. Only part of its defensive wall has survived.