Wooden Walls can be upgraded to Stone Walls in the Classical Age. The upgrade costs 200 food and 200 gold and is available to all civilizations. The research time is 40 seconds. Stone Walls have 600 hit points and 7 Line of Sight more than Wooden Walls.
The Chinese must first research Earthen Wall for 150 food and 150 gold (75 food and 75 gold for Shennong players) before they can research Stone Wall. Earthen Walls have 200 HP and 2 LOS more than Wooden Walls.
- According to an unused voice-line, information within the files, and pre-release screenshots, Stone Walls and Wooden Walls were separate, similar to the Stone Walls and Palisades, the latter as a Gold-costing, resilient structure, and the Wooden Wall as the cheap, weak Archaic Age structure that cost Wood.
- The two were mostly likely merged into the one wall-type, due to being too similar.