Original sentence: The Greater Bilbao metropolitan area concentrates a third of the total population, whilst most of the interior of the French Basque Country and some areas of Navarre remain sparsely populated : density culminates at about 500/km² for Biscay but goes down at 20/km² in the northern inner provinces of Lower Navarre and Soule
Edited sentence: The Greater Bilbao metropolitan area concentrates a third of the total population, whilst most of the interior of the French Basque Country and some areas of Navarre remain sparsely populated: density culminates at about 500/km² for Biscay but goes down at 20/km² in the northern inner provinces of Lower Navarre and Soule