Africa's longest river flows more than 4,000 miles between Lake Victoria and the Mediterranean. But the Nile's most celebrated stretch is the ribbon of blue that meanders through Egypt, waters that spawned one of the world's oldest civilizations and now offer access to many of its ancient landmarks. Most of the cruising is undertaken between Aswan and Luxor on the Upper Nile, but there are also weeklong itineraries that take guests as far as Cairo and the Delta. Either way, the Nile affords passengers a close-up glimpse of Egypt, both ancient and modern.