To access the cheat menu, press CTRL, ALT and C.

Rewards

power to the masses - All power plants become available regardless of year.
water in the desert - All water facilities become available regardless of year.
garbage in, garbage out - All garbage buildings become available regardless of year.
pay tribute to your king - All rewards and opportunities become available.

Terrain Cheats

Note: These cheats destroy buildings. Use before building.

terrain one up - Elevates all terrain 1 tile.
terrain one down - Lowers all terrain 1 tile.
terrain ten up - Elevates all terrain 10 tiles.
terrain ten down - Lowers all terrain 10 tiles.