Two massive cities on a really, really massive treadmill.
One is the suburb where everybody sleeps, the other is the
city
where everybody works.
There are about 10,000 cars all lined up on the road
between
these two cities but bolted to the ground so that they can't
move. However, when
they all gun their engines at once,
the
treadmill underneath them slowly starts to roll, bringing the
city
to them. When the city arrives, they all get out of their cars
and
work. At 5:00, they all get back in their cars and reverse
home.
Might be something you could put in a children's book or
something. Mildly interesting.