To learn more about Great Buildings, check it's tab in-game under the Build function.

Some Great Buildings are really nice to have, I would recommend aiming for St. Optional Method: It is also possible to use some of them for purchasing the last piece of Blueprint that you need, but only if you have enough Diamonds to spare though. The best way is to use them only for purchasing Diamond Expansions, especially for F2P players. Plus, it's better to get your other buildings motivated if more people will aid your city, rather than your trees (by default) for example, which is not ideal. The main reason is because when people will aid them, you'll get a lot more overall boost.

Once you unlock the Stone Circle, try to have cultural buildings instead of decorations (sell them). You can sell older buildings as you progress through the game, so that they won't take up space in your city. All buildings (except Decorations) need to be connected with your roads to function, and all roads must be connected to your Town Hall. Manage your buildings and build roads as less as possible. You can move your buildings, town halls, decorations, and roads wherever you want.

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