There are several buses that cross the bridge from Kalmar to Oland. I took a #103 bound for Ottenby, and returned on a #105. Along the way I passed several ancient earthworks, stone walls and circles and a number of old windmills while crossing the flat arable landscape. At Eketorp I visited the castle and then the Ottenby Nature Reserve near the lighthouse.
I stopped off at Gronhogen for lunch and to inspect a windmill and some walls and earthworks near the harbour, but there was nothing by way of explanation of what they represented.