Old Springfield Mall is an old version of Springfield Mall, located opposite of it.
When Homer arrived to bin Ladin family's house for a tea, he looked at their laptop and found out that Amid bin Laden was blowing up the Springfield Mall. Thinking Amid is a terrorist, Homer ran there to warn everyone (instead of Patty and Selma). However, it turned out that Amid is actually a demolitions expert who was blowing up Old Springfield Mall. Homer didn't know it, so he took the dynamite out of the old mall and threw it on the bridge which supposed to be open tomorrow, destroying it totally.