The notion of "internal improvements" ("public works") is part of economics and politics. An internal improvement is some constructable object; via which, a nation can improve its economic infrastructure. Examples of such items are: airports, canals, dams, dikes, pipelines, railroads, roads, tunnels, and artificial harbours. "Public works" is a slightly broader term, it can include such things as: mines, schools, hospitals, and the water treatment centers. In some cases, it is argued that internal improvements can be used to "solve" problems of unemployment. Opponents of internal improvement programs argue that such projects should be undertaken by the private sector, and not the public sector.