The athens daktylios (ring) used for circulation management. Vehicles with odd and even plate numbers can enter this ring on odd and even days of the month respectively.
<a href="//commons.wikimedia.org/w/index.php?title=User:Cirrus3d&amp;action=edit&amp;redlink=1" class="new" title="User:Cirrus3d (page does not exist)">Cirrus3d</a>
<span class="int-own-work" lang="en">Own work</span>, replica from Google Street View (<a rel="nofollow" class="external text" href="https://www.google.gr/maps/@37.96038,23.7371508,3a,71.7y,47.38h,97.69t/data=!3m6!1e1!3m4!1st-hb3idfsfecUMdFOSi5Nw!2e0!7i13312!8i6656?hl=el">Στην οδό Ηλιουπόλεως 10, στην αρχή του δακτυλίου // at Ilioupoleos street 10, in the beginning of the ring</a>)