Mombasa's biggest tourist attraction, Fort Jesus dominates the harbour entrance at the end of Nkrumah Rd. The metre-thick coral walls make it an imposing edifice, despite being partially ruined. The fort was built by the Portuguese in 1593 to enforce their rule over the coastal Swahilis, but they rarely managed to hold onto it for long. It changed hands at least nine times in bloody sieges between 1631 and 1875, finally falling under British control. It houses a museum, built over the former barracks. The exhibits are mostly ceramics, reflecting the variety of cultures that traded along the coast, but include other interesting odds and ends donated from private collections or dug up from sites along the coast.

The fort was the final project completed by Italian architect Joao Batista Cairato in his long career as Chief Architect for Portugal's eastern colonies. There are some ingenious elements in its design, especially the angular configuration of the west walls, which makes it impossible to attack one wall without being a sitting duck for soldiers on the opposite battlements.

Exploring the battlements and ruined buildings within the compound is interesting, though the fort feels much smaller than it looks from the outside. The Omani house in the San Felipe bastion, in the northwestern corner of the fort, was built in the late 18th century and houses a small exhibition of Omani jewellery and artefacts. Nearby is a ruined church, a huge well and cistern, and an excavated grave complete with skeleton. The eastern wall of the fort includes an Omani audience hall and the Passage of the Arches, a passage cut through the coral to give access to the sea.

Most coach tours arrive here late in the morning, so if you come early you may have the place to yourself. Many official and unofficial guides will offer their services, often for free, though a tip is always expected. Alternatively, you can buy the 1981 Fort Jesus guide booklet from the ticket desk and go it alone. At 19:00 there's a daily 'sound and light show' illustrating the fort's history, organised by Jahazi Marine.