This is a pretty nice and easy effect. Just
search for a interesting "skyline" - typically near the horizon or at middle
distances and wait for the time around either sunset or sunrise. Now meter
a very bright spot in the scene so the foreground gets totally black on
the final picture. Due to this you've to place the foreground at the lower
third of your picture - a black something is surely not interesting enough
to allow more space here while the graduated color of the sky is of major
interest here. Skylining is finally nothing else than a special "contra light"
situation but with a much more exaggerated effect.
Note: The projected slide of the image
below looks actually much better. Obviously the scanner was not able to
get all the contrast.