>>>Did I understand that Rosso should not be the best spot to cross the >>>border?
Correct./ Rosso is the worst spot to cross the border.
>>>>>..heard ST louis is much worse;
Wrong . St. Luis is a city , not a border . It is definitely hellish place (corrupt policemen , extorsions , etc) but not a border town.
>>>>>And,by the way, what is the "barage" ?
The Barrage tecnically is a raised track , which serves as a contention wall for the lake/river on the right (going to Dakar). In rainy season you can drive on the top , while in dry season you can drive on the "floor"
So people call "The barrage" to the track whcih leads you from Rosso (Mauritania side ) to Diama (small border , WHICH IS THE BORDER YOU WANT TO GO =-believeme= ).
Also , the "barrage track" follows kind of a natural park (quite amusing ) , and Its quite pictorical .
After the mauritanian side of the formalities , you cross a Bridge (which is also called "the Barrage " , and then you enjoy the Senegalese side of the formalities. Police , Douane ( get ready to shell out lots of euros ) and rip-off Insurance by a lovely lady.
you have a good day