Lighthouses

Function	Navigational aid
Substitutes	Signal stations
Influence on	Global commerce • Port architecture • Maritime safety
Power source	Steam power • Solar power
Effectiveness	Increased visibility • Improved reliability • Longer range
Main components	Light source • Lens system • Lantern room • Gallery • Staircase
Place of origin	Italy
Design principle	Solid construction, rotating light
First constructed	Mid-15th century