The Nile is the area's natural navigation channel, giving access to Khartoum and Sudan by steamer. The Siege of Khartoum was broken with purpose-built sternwheelers shipped from England and steamed up the river to retake the city. After this came regular steam navigation of the river. With British presence in Egypt in World War I and the inter-war years, river steamers provided both security and sightseeing to the Pyramids and Thebes. Steam navigation remained integral to the two countries as late as 1962. Sudan steamer traffic was a lifeline as few railways or roads were built in that country. Most paddle steamers have been retired to shorefront service, but modern diesel tourist boats remain on the river.