As you look beyond the fountain and the great lawn, you see the Grand canal which marks the extent of the gardens to the south. There is much to explore East and West too, but you need good legs and plenty of time.
The Latona fountain tells the story of the childhood of Apollo. By all accounts it was quite a feat of construction - featuring figures of lizards and turtles at ground level, peasants undergoing metamorphosis and frogs on the first tier, and frogs on the next two. Lastly, on the summit, is a bright marble statue of Latona, looking to the horizon with her back to the Palace.
Interesting narrative.