Salt mines are resource buildings in Tropico 4. Unlike other resources, salt is limitless and mines never need to be relocated. In addition to producing salt for export, salt mines will boost the production of any nearby fisherman's wharves or ranches, despite the tooltip stating that it boosts the production of ranches and canneries. Mines must not be located on resources, otherwise the building will hinder the mining process, but to maximize production, mines must be located very close.