My favorite site in Libya is Bu Njem, ancient Gholaia: a well-preserved fort of the Limes Tripolitanus. Today, this area is arid, but it has not always been that way. By building all kinds of dams, the emperor Septimius Severus changed the entire ecosystem and converted this area into a fertile zone, where sufficient food was produced to feed the soldiers in the fort.
The French archaeologists who excavated the site, first had to remove all the sand, but the rewards were great: besides the remains of the ancient buildings, there were several interesting inscriptions and dozens of ostraca, which document daily life in Gholaia.
My photos have been online since 2006, but I revisited the site last year. The new photos and an improved text are now available here. The satellite photo is also worth looking at: here.