 Fredrikstad was built at the mouth of Glomma as a replacement after Sarpsborg ( upstream) was burnt down by the Swedish Army in the 1500s.Some of the citizens stayed behind and rebuilt their old town at its original site and got their city status back in 1839.The city centre is on the west bank of the Glomma, while the old town on the east bank is Northern Europe's best preserved fortified town.