It's not clear from the article, but the site makes clear that the 'slabs' are the parts of the map colored in blue.[1] [1] http://www.atlas-of-the-underworld.

It's not clear from the article, but the site makes clear that the 'slabs' are the parts of the map colored in blue.[1] [1] http://www.atlas-of-the-underworld.org/Atlantis/ http://www.atlas-of-the-underworld.org/Atlantis/