The remains of the fortress can be visited
Saint Louis Castle

In the Lebanese city of Sidon stands the Fortress of St. Louis, also known as Qalaat Al Muizz. It was once built by Crusaders and stands on a hill, which is presumed to have been the acropolis of the ancient city.
History+
The origins of the Fortress of St. Louis date back to the time of the Crusades, when it was built by the Franks during their occupation of Sidon. It is believed that the French King Louis IX, better known as St. Louis, spent a long time in this fortress, which possibly gave it its current name. The original citadel was probably completely demolished and later rebuilt by the Arabs.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://commons.wikimedia.org/wiki/File:Sidon_St.Louis_castle.jpg?uselang=de
This description draws on the facts documented in the linked Wikipedia article; Wikipedia content is licensed under CC BY-SA 4.0. Wording and editing: Mobile History.
Location: 33.5604, 35.3706