At Red Rocks, time and imagination produced a long history of naming and renaming formations, with gateway rocks and others compared to ships or named for parks, caves, and other features. As cracks became crevices and then larger spaces such as grottos, caves, and labyrinths, they inspired fanciful names including Fat Man's Misery and Demon's Grotto. In the early 1900s, when J.B. Walker called his park Garden of the Titans, many features took names from ancient Greek gods, including Rock of Cronus, Rock of Mnemosyne, Cave of Saturn, Spring of Rhea, and Rock of Tethys. Tunnel Rock was once Lizard Head Rock; a small poised rock was known as Seat of Pluto and the Toadstool; Ship Rock on the south was once Rock of Coios or Coeus and had a Lover's Leap on its north edge. Creation Rock, north of the amphitheatre, may hold the oldest name applied to the highest rock; by 1901 it was called Mammoth King Rock, during the Titan era it was Rock of Cronus, and its High Cave was renamed Cave of Saturn. Stage Rock has hosted concerts since 1908, and Rock of Tethys lies just east of it but has no current name. Ladder Cave Rock was also called Seven Ladders Rock and Rock of the Erinnyes, named for climbs once constructed inside it, and interior features also bore names such as Jacob's Ladder and Toboggan Slide. Nine Parks Rock, also called Rock of Mnemosyne, contains nine openings called parks, grassy open spaces within a large outcrop where moisture gathers, plants grow, and animals find small islands of habitat. Picnic Rocks also carried names including Rock of Cronus, Promontory Rock, Forbidden Climb, Coves of the Melian Nymphs, and Lover's Leap. Across the valley, Gog and Magog likely received their biblical name in the late 1800s when the area was known as Garden of the Angels; Gog, known as Sphinx from the east, is also a smokestack on a rock often called the Sinking Titanic. Frog Rock stands at the south end of the park, with a smaller nearby feature called the Toad, while Park Cave Rock, also known as Crown Rock, is the easternmost rock. The sinking of the Titanic in April 1912 also left its mark in names such as Sinking Titanic and Iceberg.