There are a few possibilites.
1) The Nile River runs through Sudan
2) The White and Blue Nile rivers meet and Khartoum and become the Nile River
3) The "Sud" swap-lands of southern Sudan
amongt others...
Its a famous landmark there.
Russia's most famous landmark is St.Basil's cathedral.
The most famous landmark in Rome, Italy is thought to be by most The Colosseum.
the most famous landmark in Turkey is entirely your decision it depends on your opinion!
The Eiffel tower is the most famous Parisian landmark.
I believe it is the Parthenon the statue of Athena.(This might not be the most famous landmark in Athens but it is very famous)
It is an opinion of what the most famous is so there is really no answer.
Alhambra
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It is Abuja
Most likely The Coliseum