<P> The stadium 's track and field arena is excavated out of the soft clay found on the site , around which is permanent seating for 25,000 , built using concrete `` rakers '' . The natural slope of the land is incorporated into the design , with warm - up and changing areas dug into a semi-basement position at the lower end . Spectators enter the stadium via a podium level , which is level with the top of the permanent seating bowl . A demountable lightweight steel and pre-cast concrete upper tier was built up from this `` bowl '' to accommodate a further 55,000 spectators . </P>
<P> The stadium 's track and field arena is excavated out of the soft clay found on the site , around which is permanent seating for 25,000 , built using concrete `` rakers '' . The natural slope of the land is incorporated into the design , with warm - up and changing areas dug into a semi-basement position at the lower end . Spectators enter the stadium via a podium level , which is level with the top of the permanent seating bowl . A demountable lightweight steel and pre-cast concrete upper tier was built up from this `` bowl '' to accommodate a further 55,000 spectators . </P>
what was the london olympic stadium built on
what was the london olympic stadium built on
soft clay
soft clay