Destroyed in the Biafran civil war, Onitsha has since been rebuilt. The city is famous outside Nigeria for its Onitsha Market Literature—short moralistic pieces about life in the region (a few of these pamphlets are, in fact, sold at the market). Onitsha is less a city than it is a collection of markets (there are seven major ones).
It serves most of southeastern Nigeria. Onitsha has a rich ritual tradition, including a yearly installation of the Obi Onicha (divine king of Onitsha) and weekly masquerade performances. These events generally require an invitation from a local person, though you might get lucky and be in the right place at the right time (masquerades periodically burst out of compounds and parade through the streets and markets). The tasty, spicy local cuisine is based on fresh fish from the Niger River. The river is very wide there, possibly more than a mile/kilometer.
230 mi/370 km east of Lagos.