Sumburgh is the southern tip of Mainland in Shetland, where the airport runway, old stone settlements, bird cliffs, and ferry pier all crowd into a small strip of land. It is not really a town, and it is best treated as a compact Shetland feature rather than a city stop.
The spare-day case is strong. Jarlshof alone is one of Scotland's great archaeological sites, with layers from prehistoric houses to Norse and later farm buildings. Nearby Old Scatness and Ness of Burgi add more Iron Age texture.
Then the road climbs to Sumburgh Head, with a lighthouse, visitor centre, and seabird cliffs. If you have a car on Shetland and the weather is fair, the area makes one of the islands' easiest half-day circuits.