From Wiki Grepolis
The Timber Camp produces wood that can be used to build units and buildings for your polis. They work in the dense woods on the boundaries of your polis. The higher the level of the Timber Camp, the more usable wood gets produced per hour.
The Timber Camp is your key source of wood. It will produce wood, even when you are offline, for you to use in the building of buildings, the training of units and the researching of technologies. The higher the level of the Timber Camp, the more wood produced hourly.
None, the Timber Camp is available from the beginning of the game.
The maximum level of the Timber Camp is 40. The Timber Camp's apperance changes depending on the level of the Timber Camp.
|Under Construction||Level 1 - 13||Level 14 - 27||Level 28 - 40|
The Timber Camp is great source of wood income (as shown in the below table). However, some things can change the output of the Timber Camp, such as Merchant (not shown on the below table) and the productivity of your island. Each island produces 10% more of a resource and 10% less of a resource; coming into effect after level 20 (meaning all levels before produce the same amounts of resources). This is in the below table and is denoted by column. You can find out if your island is +/- by looking at the icon in the middle of your island.