The arid capital city (pop. 4,495,000) of Sudan, at the junction of the White Nile and the Blue Nile, merits a stay of at least two nights. It's an interesting place to walk around, snoop in shops and people-watch. Also take a ride on the Nile (in Khartoum or in nearby Omdurman), and then visit the National Museum (antiquities from around the country), ethnological museum (tribal artifacts) and natural-history museum (local bird and wild-game displays).
The most fascinating sight is the juncture of the White and Blue Nile Rivers. Al Mogran Family Park, an amusement park, is located at the point where the rivers flow together. After spending time at the confluence, take a ferry to
Tuti Island for a look at a typical rural village. Consider excursions to Jebel Aulia Dam (great spot for bird-watching, fishing, picnics and people-watching) and the Sabaloka Gorge (the Nile's Sixth Cataract—it's a three- or four-hour drive each way). Other trips—by four-wheel-drive vehicles or local buses—can be made to the ruins at Meroe and Shendi; they can be seen on a day trip, but we really recommend taking them in during a three-day trip.
Note: A permit is required for all travel outside Khartoum. These can be obtained from the Passport and Immigration Office, Ministry of Interior in Khartoum.