The Phasael Tower, Hippicus Tower and Miriamne Tower are three towers in Jerusalem situated close to where the Jaffa Gate is today. These towers protected the main entrance to the city. Phasael tower was named after Herod's brother Phasael, Hippicus was named after Herod's friend who fell in battle, while Miriamne tower was named after Herod's wife Mariamne. The only remains of these towers today is the base of Phasael's, found in the Tower of David.
When the city was razed in 70 AD, only one of Herod's three towers - Phasael, in the northeast corner - remained standing. During the Byzantine period, the tower, and by extension the Citadel as a whole, acquired its alternative name - the Tower of David - after the Byzantines, mistakenly identifying the hill as Mount Zion, presumed it to be David's Palace. The Citadel was gradually built up under Muslim and Crusader rule and acquired the basis of its present shape in 1310, under the Mamluk sultan Malik al-Nasir. Suleiman the Magnificent later constructed the monumental gateway in the east that you enter through today. The minaret (no public access), a prominent Jerusalem landmark, was added between 1635 and 1655, and took over the title of "Tower of David" in the nineteenth century, so that the name can now refer to either the whole Citadel or the minaret alone.
On the site itself, from the top of the Phasael Tower there are good views over the excavations inside the Citadel and out to the Old City, as well as into the distance south and west. On the way up, a terrace overlooking the diggings has plaques identifying the different periods of all the remains. These include part of the Hasmonean city wall, a Roman cistern, and the ramparts of the Ummayad citadel, which held out for five weeks before falling to the Crusaders in 1099.