Tips to plant academy

filthyrobot suggested that we put an academy on a high yield tile to make use of the fact that our city is already working on it. I like this idea and usually use it. But i noticed that planting one on a hill or a tile that yield lots of hammers will cost 2 hammer, instead of 1 if put on farm. So I just want to ask vets here if there are better/optimal tiles to plant an academy.