classnormal the lighthouse of alexandria was built as a beacon to sailors navigating the treacherous harbors of alexandria and the island of pharos not only was it the tallest building on earth but the reflection of its mirror could be seen more than 35 miles offshore the lighthouse was conceived in 290 bc and stood until two powerful earthquakes in 1303 and 1323 ad seriously damaged it an egyptian sultan built a fortress with the rubble in 1480 ad photo courtesy wonderclubcom