This 18-piece upgrade kit for Teotihuacan: City of Gods includes:

• 15 decorations from the base game of Teotihuacan
• 3 special promo decoration tiles

The tiles are made of wood and painted on one side. They are about half the thickness of the main pyramid tiles. 

Instructions for matching the special Decoration symbol: For purposes of matching the covered icon below it, this symbol counts as a generic icon. However, when covering a generic icon, in addition to scoring 1 Victory Point as normal, you may advance on any one temple of your choice.