Asked by: Kerry Waters, by email
Probably the Tower of Hercules lighthouse, which dates back to Roman times and stands on a headland near the city of La Coruna on Spain’s northwestern coast. The original Roman lighthouse – called a pharos – was built in the 2nd century AD, with a spiral wooden ramp up the outside for fuel to be carried for burning at the top.
Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.
