The Story of the Stolen Cannon
Grant Park once had four Civil War cannons decorating the park. In 1887 the city of Atlanta asked for four inoperable cannons to display at Fort Walker in Grant Park.

View of Grant Park cannons at Fort Walker - 1895 (Image from Atlanta History Center)
By 1984, the cannons were in sorry shape, vandalized, their wooden carriages in danger of collapse. The cannons were restored and moved. Two went to the Cyclorama, the Battle of Atlanta display at Grant Park. The city stored a third at City Hall East, where it was stolen but later recovered. The fourth cannon went missing...
On February 8, 2010 the missing cannon was found among many stolen items on a Spalding County farm. The man in possession of the cannon was only 20 years old of the time so he was too young to have originally stolen the cannon. In 2010 the missing cannon had estimated value of $200,000.
After some time the cannon was returned to Atlanta Cyclorama in Grant Park, where it sat in its crate in the entry foyer for a few years. In 2014 the Atlanta History Center struck a deal with the City of Atlanta to relocate the artifacts in the Cyclorama to the Atlanta History Center. The Atlanta History Center had cannon reconditioned and will be displayed there.
Cache Information
You are looking for a Micro cache. Hidden easily since the hardest part will be avoiding the muggles. Parking is free on the street but pay in the zoo lot.
Additional Information on the Stolen Cannon and Fort Walker
AJC - Authorities mystified by stolen Civil War cannon
Friends of GA State Parks and Historic Sites - Cannon Comes Home
Wikipedia - Fort Walker (Grant Park)