"The land is sacred. It's where nine people died," Mayor Joseph P. Riley said.
The Sofa Super Store showroom and warehouse were gutted by the June 18 blaze, the worst single loss of U.S. firefighters' lives since the Sept. 11 attacks.
Riley said he spoke to store owner Herb Goldstein, who agreed with the idea. Riley said the two talked before the mayor traveled to Indiana for the last of the firefighter funerals.
The land, about 2.5 acres, is on a busy commercial strip lined with car dealerships, repair shops and fast-food chains.
Riley said the land should never contain another structure.
"This should be a passive place in memory of these nine heroes. It will be a place for our citizens to come, for firefighters (and) for friends and relatives of our deceased firefighters."
Federal officials have traced the fire to a trash bin on the loading dock, but they have not released a cause. On Tuesday, a city official said a roof above the loading dock was built without a required permit.
The last of the funerals for the nine fallen firefighters was also held Tuesday.