From Wiki Grepolis
These three resources are at the heart of Grepolis and are essential for progressing in the game. You build up the production buildings to increase the rate at which the resources are produced. With them you can build new buildings in the Senate, new soldiers in the Barracks, new ships in the Harbour and you can research new technologies in the Academy.
|Wood||Gathered in the Timber Camp.|
|Stone||Gathered in the Quarry.|
|Silver||Mined in the Silver Mine.|