Successfully complete the game with the indicated number of 'Gold' ranks to unlock the corresponding bonus level. To access them, press X at the level selection screen to display the 'Lost Levels' level selection screen.
Ancient Rome - Praetorian Camp: 3 'Gold' ranks
Ancient Rome - The Forum Romanum: 5 'Gold' ranks
Ancient Rome - The Forum of Trajan: 7 'Gold' ranks
Ancient Rome - Addressing the Senate: 9 'Gold' ranks
Ancient Rome - Caesar's Sanctum: 12 'Gold' ranks
Feudal China - The Silk Road: 15 'Gold' ranks
Feudal China - The Gate of Supreme Harmony: 18 'Gold' ranks
Legendary Atlantis - The Steam Tower: 22 'Gold' ranks
Legendary Atlantis - The Geothermal Tunnels: 24 'Gold' ranks
Legendary Atlantis - The Corridors of Power: 26 'Gold' ranks
The Gallery: 31 'Gold' ranks