Mining technique at Eupalinos tunnel in vertical cross-section, at the expected point of meeting of the two tunnels, to make sure that one tunnel will meet the other, covering small mistakes in the calculations of the engineer (also see the same technique applied in horizontal cross section at <a href="//commons.wikimedia.org/wiki/File:Eupalinos_horizontal.JPG" title="File:Eupalinos horizontal.JPG">File:Eupalinos horizontal.JPG</a>
Designed by User:FocalPoint, after Hermann J. Kienast (The aqueduct of Eupalinos in Samos), Athens 2004, publication of Greek Ministry for Civilisation. Vectorized by Magasjukur2
CC BY-SA 3.0
<a href="//commons.wikimedia.org/wiki/File:Eupalinos_vertical.JPG" title="File:Eupalinos vertical.JPG">File:Eupalinos vertical.JPG</a>