[reading: Samuel R. Delany, "Babel-17"]
A waterfall day, starting with Seljalandfoss and a smaller waterfall nearby.
Then on to Skógafoss.
The town of Skógar also has a folk museum, which seems to be international standard terminology for "eclectic collection of junk" (although still interesting for all that).
Icelanders seem very fond of sculpture; most towns seem to have a piece or two, even very small towns. (Every town also seems to have an interestingly-architected small churchI've seen many innovative designs).
On the way back, there's a stop for ice cream in Hveragerði. The trip notes have this to say about Hveragerði:
Minor earthquakes are common and quite harmless. In the middle of the town the ground is too hot for buildings and a fence has been built to keep pedestrians safe! We can either stroll around this green oasis or use the opportunity to soak ourselves in the wonderful geothermal baths of Hveragerdi.
The reality seems to be rather more along the lines of the Rough Guide description:
There's not a huge amount to see in Hveragerði itself, though some fine hiking hereabouts might encourage a stopover.
Finally, back to Reykjavík for a puffin dinner at Lækjarbrekka.