The Olive Tree is a email-only gift categorized into Happiness. It boosts the happiness of your empire by 100. It is animated (at highest magnification you can see the figure slightly nod and then blink) and there is an old man sitting on a bench near a twisted olive tree. It makes a 2 times 2 footprint.
Most likely the "Old Man" is the philosopher Socrates. Socrates once said all he needed for happiness was a loaf of bread, some olive oil to put on it, wine, and a tree to sit under.
Despite looking like a Decoration, it can not be placed in Storage.