Yes, it is imperfect like all man-made things! One lintel has an extra hole in it; one stone had a cracked bottom but was packed and used anyway (this flaw led to an early collapse.)
Rocks were used to build the monument, which is a natural object, though man put it together to form Stonehenge. In quick answer, no. It is man-made.
No, Stonehenge was created by an ancient race of people.
Stonestone
rocks
See related link for information about Stonehenge.
Stonehenge
I dont know what its made out of but its made near StoneHenge
The observations made at Stonehenge were of a simple kind carried out for the religious and ritual practices of the people.
Sarsen and bluestonelimestone
Stonehenge.
Big ones. :)
Stonehenge has never actually been discovered because it was never lost. Since it was built people have always known were it was, even the Romans knew of its existence. The only real mystery is that knowbody can be absolutely certain why it was built and what its indended purpose was.