Once a small Yoruba settlement, and then a harbour to export slaves by the European powers, Lagos today is West Africa's largest city. Big, brash and bold, it's traffic-congested and heaves with millions of people. Not all areas are safe to visit, and the traffic, crowded streets, noise and pollution can be overwhelming. But Lagos has atmosphere, and the few tourists that do go find a culturally rich, dynamic city with a frenetic pace of life. This, certainly, is the most exciting destination in Nigeria.

Lagos is made up of a clutch of islands, a tangle of bridges and freeways, and vast residential areas spreading across mainland Lagos State. Lagos Island, the commercial core, merged to Ikoyi by landfill, is separated by the Five Cowrie Creek from upmarket Victoria Island, which is again merged by landfill to the Lekki Peninsula to the east. This, collectively, is The Island, linked to the Mainland by the Third Mainland Bridge that stretches across Lagos Lagoon.

The network of roads makes Marina the most convenient part of Lagos Island to access Apapa docks, the Mainland and beyond. This long shoreline of towering office blocks is the traditional commercial hub. Although focus has since shifted to Victoria Island, Marina is still home to the Central Bank of Nigeria and ornate, Brazilian-style villas, a rare legacy of Nigeria's colonial history. The Cuban Lodge is one of many such buildings along Odunlami Street; the Water House on Kakawa Street was built by another Brazilian returnee, and said to be a replica of his home in Salvador.

Further north on Martins Street is the Shitta Bey Mosque, also in Brazilian style, built in 1892 for a rich Muslim from Sierra Leone. At the same time, the British were expanding the local infrastructure, transport, electricity and telephones. Their old colonial buildings still line Broad Street to the west of Tafawa Balewa Square, a hub of official buildings once used by Nigeria's ministries until the government moved to Abuja in 1991. Known by locals as TBS, it stages rallies, religious gatherings and the Independence Day celebrations on 1 October.

TBS centrepieces the south-east corner of Lagos Island, bordering Ikoyi, and contains the city's main sight, the National Museum (King George V Road, Onikan, 01 876 4522, closed Sun). Opened in 1957, it houses bronze sculptures and ivory carvings from Benin dating back 300 years, and the bullet-ridden black Mercedes in which the local president was assassinated in 1976.

Walking is the easiest way to see this part of Lagos Island, passing the Gothic Renaissance Holy Cross Cathedral, the Christ Church Anglican Cathedral with its Brazilian features, and the many market stalls. The Jankara market area has the best textiles.

For restaurants, bars, boutiques and galleries, head to Victoria Island, easily negotiated by taxi. At its eastern end, the Lekki Peninsula offers a clean beach and the Nigerian Conservation Foundation Centre (Km19, Lekki-Epe Expressway, 01 264 2497), a 78-hectare reserve of crocodiles, monitor lizards and mona monkeys.

• Tourist information: Nigeria Tourism Development Board, 2nd floor, Hanaco Plaza, 113 Ikorodu Road (01 493 0220, www.nigeriatourism.net).