An explosion damaged the top of a historic, spiral minaret Friday in the central city of Samarra, blowing a two-meter-wide by two-meter-high hole in the ninth-century structure, police Lt. Qasim Mohammed said. Witnesses said two men climbed the 170-foot-tall (50-meter-tall) minaret, then returned to the ground before the explosion occurred. The minaret is a symbol of Samarra's past glory, the only remains of a mosque dating back from the Abbasid Islamic dynasty. It is featured on Iraq's 250-dinar bill. Also Friday, witnesses said a car bomb exploded outside a U.S. base in Ramadi, near a convoy at the base's gate. The U.S. military and Iraqi police did not immediately have information on the blast.