Niokolo-Koba is probably the best game park in West Africa, though it's not in the same league as the parks of eastern or southern Africa. Niokolo-Koba is rarely packed with tourists, in part because of its inaccessibility. The park is accessible only during the dry season (December-May) and is best reached by road (a long drive from Dakar). Within its boundaries are lions, hippos, baboons, elephants, turtles, more than 300 varieties of birds and many other animals, including the derby eland (the world's largest antelope).
Simenti is the place to base yourself within the park; its recently remodeled hotel overlooking the Gambia River offers pirogue rides, four-wheel-drive excursions and guided walks within a limited area. For safety purposes, it is illegal to walk around the park without a guide. With very little effort you can see crocodiles, hippos, warthogs, monkeys and many kinds of birds; the evening boat ride is probably the most relaxing way to see the animals in their element.
If you have time after visiting the game park, you can take a side trip to the waterfall at Dindefelo, about 20 mi/30 km from Kedegou (a three-hour drive from Tambacounda). At the base of the Dindefelo waterfall is a refreshing pool where you can take a dip and cool off after the 1-mi/2-km walk to the falls from the village campement (similar to a bed-and-breakfast), only run by the community. Niokolo-Koba is 375 mi/600 km southeast of Dakar.