The Arboretum de Sibang is a sixteen-hectare patch of primary rainforest preserved on the inland side of Libreville. Originally planted by the colonial forestry service in 1931 to study Gabonese timber species, it now functions as a small nature reserve where you can walk a network of trails through tall canopy.
You will see hornbills, mona monkeys, and a remarkable diversity of trees, most labelled with French and Latin names. Entry is cheap; a guide can be hired at the gate. Wear closed shoes and bring insect repellent.