After you get further along in the game you may notice a golden idol off in the fog of the land you have yet to explore. If you use pickaxes and explore over to these idols they give you bonuses in your resource earnings. The first one to be found is the XP idol and will boost your XP by 5% just for digging it out. You can upgrade idols to earn even higher boosts. Definitely helpful to be able to level up quicker in higher levels. There are several types of bonus idols that earn you more silver from each action and even one that reduces watering time on your crops.