Symmes Monument (Hollow Earth Theory) is in Symmes Park or Ludlow Park, bordered by South Third, South Fourth and Sycamore streets in Hamilton. It honors Captain John Cleves Symmes and his Hollow Earth Theory. "I declare the earth is hollow, and habitable within," said John Cleves Symmes in summarizing his "Theory of Concentric Spheres and Polar Voids" to a doubting scientific world in the early 1820s. His theory is commemorated by a monument -- topped by a replica of a hollow earth -- in a Hamilton park, formerly a pioneer cemetery, between South Third, South Fourth and Sycamore streets. Symmes believed plant and animal life existed within the opening in the hollow earth. The opening was called the Symmes Hole. The former army officer tried to persuade the U. S. Congress to finance hollow-earth exploration. After an exhausting lecture tour on behalf of his theory, Symmes died May 29, 1829, on his Butler County farm. He was buried in the Hamilton cemetery, which Israel Ludlow had provided when he laid out the town in the 1790s. The theorist was the nephew of Judge John Cleves Symmes (1741-1814), who promoted settlement in this region after buying land north of the Ohio River between the Little Miami and Great Miami rivers. When Greenwood Cemetery was created north of Hamilton in 1848, many of the remains in the Hamilton graveyard where removed to the new cemetery, but Symmes body remained in its original location. In 1873, his son, Americus Symmes, obtained permission to erect a monument in the Fourth Ward park. A $16,000 renovation -- commissioned by Historic Hamilton Inc. -- was completed in 1991. The former cemetery was named Ludlow Park in an ordinance adopted June 18, 1890, by Hamilton City Council.