The Fossil Lawn is to the east area of Ribular Island in Fossil Fighters: Champions. It has a Fossil Cannon, and allows the Hero to recieve Bonus Data events. Todd can be battled here in the post-game.
A similar Fossil Lawn can be found in the Park Area of Vivosaur Town in the original Fossil Fighters. This is where the Fossil Rocks received during Cannon fire land. In addition, bits of "Fossil Haiku" can be found with the rocks. No one knows exactly where the Haiku comes from, but many players have speculated the stuttering Attendant near the Cannon writes it.