The Parliament, the Executive Government and the Judicature
Explanation:
At the center its weight is zero. Or you can argue by symmetry: if the weight is not zero, in what direction would it act?
The name for such a hole is "caldera" which is a word of Spanish origin meaning "a pot" or a "cooking pot" (thing of cauldron!) - and this word is used because it resembles the shape of this hole.
Often the Calderas are filled with water forming lakes and often there is an island in the middle of the water.
