To outline the most important of them, here is a short list.
- Greece has a grid of regulations to protect its cultural heritage. Permission is needed from the archaeological agency, regarding the excavations.
-If planning to build outside the city limits, certificates are needed that the plot is not part of a forest, a protected "natura" area, an area that could be planted. Also that it is adequately away from rivers, lakes, high voltage cables, highways etc, etc. The list is quite long to mention every different case here.
-Building inside the city's limits is somehow easier since, in most of the cases, all the above are not required. But still, there are some restrictions.
-Islands (but not only) have special architectural types of buildings to be followed (such as the white painted walls and the blue windows, to the Cyclades).
Unfortunately, there is nowhere to search and find all this information. Each case is different. Even an experienced engineer who deals with this kind of stuff finds it quite difficult to have the whole picture because the laws are so complicated and in many cases contradictory, that special skills are needed to understand them.
The wisest thing to do is to address to a local engineer to help you out. This is the only way to be sure that you will avoid any complications. Even if you want to keep your architect or structural or mechanical engineer, to do the design, you still have to do this.