Skeiðarársandur, a vast sand desert about 20 by 30 km between the districts Fljótshverfi in the west and Öræfi in the east. It is said that there were once many farms in this area, but these were destroyed by tremendous floods from Grímsvötn in Vatnajökull breaking their way under the glacier. The largest of these Skeiðarárhlaup, as the floods are called, have been compared with the Amazon river. In 1974 bridges were built across the rivers Núpsvötn, Sandgígjukvísl and Skeiðará thus completing the main highway round Iceland. Considerable volcanic activity in Vatnajökull glacier in 1996 destroyed one bridge and damaged another. Much quagmire remains and travellers are warned that great care should be taken and no attempt made to drive off the main road in this area.