At the top of the middle spire of the Gant Bridge, there is a plaque on the eastern side. The sign reads "There are no Easter Eggs up here. Go away." Ironically, this makes the sign an Easter egg.
The sign can only be accessed using an aircraft, but the Jetpack is recommended. The area the sign is in will be closed off with an invisible wall until the player unlocks Las Venturas, after the mission Yay Ka-Boom-Boom. It serves no other role other than being a humorous message for the player to discover.