The train carrying iron ore from Zouerate to Nouadhibou has been the longest in the world up to the 90'. It is one mile long, pulled by 5 diesel locomotives.
It is possible to go to and fro Zouerate in a coach attached to the train. You can even travel first class. The travel lasts 13 hours in the desert.
Be carefull, it is almost not possible to plan the travel because they don't have fixed schedules.
Nouadhibou had been isolated from the rest of the country until Quarter 1 2005. Instead of one day, you only need 4 hours to go from Nouakchott to Nouadhibou.
The road is in perfect conditions. Be sure to have enough diesel/petrol because there are 465 km without possibility of tanking. (This is the longest part of the road without filling station between Tangiers and Lagos).
lots of people use this poor animals to carry hundreds of kilograms under strong sun and for hours in a row. Although if you are very tired you can always jump to one of the carriages and people will smile at you. Go out whenever you feel like to. Ask waving your hand pointing to the him before you jump of course.
Planes leave to nouakchott twice a day for about 13000UM 35 min flight. There are flights every Monday to and from Casablanca and twice a week to Las Palmas with Air Mauritania. There are some Antonov fish flights leaving every morning of thursdays and Mondays.
A bicycle can be a very good way of going around the city. You'll have to be careful with the place you park it because the lack of care will make your bike disapear.
Also be careful with crazy drivers. Remember that driving licenses can be bought underground and even in driving schools you can get the license just paying 30000UM. No driving skills need.
Buses in town are this old Mercedes vans. Prices are 20UM for a trip. You just wave to make it stop and when you wish to go out just hit hard on the ca or even better and like locals do, get a coin and hit it against the metal of the truck. A good thing to do is always give your sit to an elder person. They will take that very deep and you'll win their respect.
Buses can take an full load of people inside that can go up to 30.