The "scar in the face of Paris" has an upside
It gives you the best view, for you wont be able to see the tower itself.
This 330m high building in the middle of Paris is despised by everyone. Which is why people like going up to the top: So you can take pictures of the city and not have it in there.
Metro Montparnasse Lines 4, 6, 12 and 13.