This lighthouse has a sophisticated rotary mechanism with 12 parabolic mirrors. This fact, combined with its height reaching 29.5 metres, gave a luminescence that was over 20 miles –this is why the folk tradition wanted its shine to be distinguished up to Izmir!
The lighthouse on the islet Didimi (Gaidaros or Grado), opposite the entrance to the port of Ermoupoli, is stone-made. It operated in 1847, but its construction began in 1834 in designs by Bavarian architect Erlacher who built the marble interior staircase as well. It was the first lighthouse in the Aegean with rotating mechanism and it was funded by the state in the period of King Otto. Along with the lighthouse of Spetses (1837) it belongs to a special type that has the home of the lighthouse keeper in a ground floor building.