 The bridge surface is located only 30 – 40 cm ( 11 @.@ 8 – 15 @.@ 7 in ) over the arches ' apex , is 3 @.@ 55 – 3 @.@ 70 m ( 11 @.@ 6 – 12 @.@ 1 ft ) wide , increasing towards either end at 4 @.@ 30 m ( 14 @.@ 1 ft ) and projects ca . 10 cm ( 3 @.@ 9 in ) over the superstructure on either side . It is paved with large and irregular limestone cobblestones , although smaller pebbles have been used in the repairs at the two semicircular arches . 
