A prestige project is a costly endeavor such as a space program or the construction of a steel mill or hydroelectric dam that a government pursues for the sake of the country's glory, at the expense of leaving more urgent priorities unaddressed.
For example, North Koreans have often starved while their government invested money in rockets and nuclear weapons, neither of which were urgently needed to secure the country's borders. China's aircraft carriers have also been described as a prestige project, since their military usefulness is rather limited.
Prestige projects often become run-down over time. The reason is that there is a huge photo opportunity when it opens, but no photo opportunity for applying some new paint and keeping it in good repair. The Three Gorges hydroelectric dam being built on the Yangtze river is already showing signs of cracking. Muammar Gaddafi carried out the world’s largest irrigation project, known as the Great Man-Made River project, to make water readily available throughout Libya, when it would have been much cheaper to develop desalination plants. The German railway project "Stuttgart 21" has also been described as a prestige project.