Natural harbours and battleship-sized docks

What makes the world's best natural or artificial harbours useful for major naval docks?

Depth, approach routes, and the ability to build large docks matter alongside the harbour itself; a battleship-sized dock is useless if the ship cannot reach it.

Dock dimensions alone are not enough: a battleship must also reach the facility through a sufficiently deep river, channel, or harbour approach. Natural protection, navigable depth, and room for large docks all affect whether a site can support capital ships. Britain benefited from an unusually large number of suitable locations for its size. Geography did not create a naval base by itself, however, because basins, locks, cranes, and repair works still demanded sustained investment. A harbour on a map becomes useful to a battle fleet only when ships can reach and use its maintenance works.