This stop is called Back to Rondane, which is a slight misnomer, because the point actually lies in Østfold on the eastern side of the Oslofjord, near Rygge and the town of Moss. Rondane's high plateaus are a long day's ride north. What you have here is a very different side of Norway, gentle, farmed and close to the sea.
Moss, with about thirty-four thousand people, is the main town, and it is a good place to know. It sits on a narrow strait with a working harbour and an industrial past in paper and iron, and its main claim to fame in the history books is the Convention of Moss in 1814, when Norway's brief independence after the break with Denmark was settled in a deal that brought it into a union with Sweden. A car ferry runs from Moss across the fjord to Horten, which is a useful shortcut if you are heading to the west side, and the crossing gives you a sea view for free.
Rygge nearby was home to a military air base, later a commercial airport that closed to passenger traffic in 2016, so the sky overhead is quieter than it used to be. The terrain around is gently rolling farmland, with big grain fields, small woods and fjord inlets, and in late summer the whole thing smells of cut hay. It is not dramatic, but it is a pleasant change from high mountain roads.
Riding is relaxed. The E6 runs close by and carries heavy traffic, but the smaller roads to the coast are quiet, with mild bends and occasional farm tractors. Keep to the limits, as Norwegian traffic cameras are everywhere, and watch for deer at dawn and dusk. The weather is milder than in the mountains, though rain can sweep in from the Skagerrak.
For fuel and food Moss is the obvious answer, with several stations and plenty of cafés near the harbour. Smaller places along the way may not be open late, so do not rely on them.
Come in early summer for the long evenings, when the light lingers and the fjord looks like polished metal. A coffee on the harbour front in Moss is a fair reward for a day on the road.