|Effect||Upgrade all units to current best unit in their lineage|
Leonardo's Workshop can be built when the player discovers Invention. When completed, it upgrades all the player's units to the most advanced level they have discovered. For example, if the player has discovered the Gunpowder technology and builds this wonder, all of his or her Archers and Pikemen will become Riflemen. Horsemen, Knights, and some upgraded Warriors and Legions (if they have March, Blitz, or Infiltration) can become Tanks. Archers, Warriors, Pikemen, and Riflemen can become Modern Infantry. Galleys, Triremes, and Galleons can become Cruisers, but not Battleships. Any embarked units will also upgrade (except the Ranger Militia, which remain unchanged). Catapults, Trebuchets, and Cannons can become Artillery units. Air units and Submarines are not affected.
Any upgrades, such as veteran status, Blitz, or Loyalty, will remain. Any units in cities acquired later in the game by flipping will remain whatever they were and will not be upgraded.
It is best to build this wonder just after discovering Mass Production, Combustion, Steam Power, and the Automobile (though if the player has no or few Catapults and Cannons, the Automobile can be researched later).
Note that this wonder provides its benefit only once, so it cannot be cancelled and will not continue to upgrade units into more modern ones.