This is an artist's Impression of a bold plan: The Imperium was considering at
one point to build a Ringworld.
If you note, the interior ring is cut in ovals, so as to provide a varying
degree of sunlight across the Ringworld laterally.
Thus regions in the interior of the Ringworld will get more sunlight, and thus
be warmer, and regions toward the rims
will get less, and be colder. This is to promote a wider variety of species on
the construct itself.
Partly for additional variation, but mostly for the propaganda value,
the edges of the oval were dagged to make them appear as the Imperial Sunburst.