During the Ptolemaic Kingdom of Egypt, the Lighthouse of Alexandria on Pharos Island was one of the Seven Wonders of the Ancient World. For years, it was one of the tallest man-made structures on the planet and people came from far and wide to admire the feat of architectural prowess. A series of of three earthquakes from 956 and 1323 decimated the structure, which was ultimately abandoned.

In 1477, Sultan Al-Ashraf Sayf al-Din Qaitbay ordered a fortress to be built on top of the foundations of the former lighthouse. During the two-year construction, stones from the remnants of the lighthouse were used as construction materials. Today, the citadel is the only chance to glimpse a fragment of this long-lost wonder. 

At the front entrance of the citadel, you'll notice that slightly darker rocks frame the doorway—these were salvaged from the lighthouse. This gives the traveler a chance to touch or even sit on part of the ancient lighthouse (there are two large stones that sit in front of each side of the entrance).

Aside from its unusually storied building components, the citadel itself is a sight to behold. The structure survived the Ottoman conquest, Napoleon's campaign, and the Pashas of Egypt and into modern day. The citadel is perched over Burullus Lake, offering unimpeded views of both the city and the Mediterranean Sea. 

Curiously, another long-vanished piece of the ancient world lies beneath the waves here. Cleopatra's palace was submerged by yet another earthquake and now rests 16 feet underwater.