The Velky Strahovsky Stadium in Prague, Czech Republic, also known as Spartakiadi Stadium, was place of the biggest sports event in the world. About 240.000 people were in this stadium for the Spartakiade in 1967.

Unfortunatelly it is in low resolution but even that you can see it is about 400m long. Total field size 60.000 m2

For comparison, on the left from the Strahov stadium, you can see normall size football stadium.

Sorry, but the biggest sports event in the world is consistently the Indianapolis 500 with 400,00+ attendees... The Brickyard also holds the title for the largest sporting venue.

It measures 0.94 miles (1.52 km) by 0.44 miles (0.71 km) for a square footage of 11,530,041ft2 (1,079,200 m2)

Sorry, but Indianapolis doesnt compare with the corwds Silvestone or sometimes the superbike gets, those or 500,000+

Guys, I was posting biggest stadium (see subject) and biggest sport event on the stadium.
For sure it can not compare with the events like car racing, horse racing, etc.

I was at Silverstone for the 2005 sold-out British Grand Prix, and it definately does not hold half a million people. 150,000 at a push.

The biggest stadium that a football game could sensibly be played and watched in is the Rungnado May Day Stadium in Pyongyang, North Korea. This has 150,000 seats - bigger than the current capacity for the Maracana in Rio.

Here is a link:

http://www.worldstadiums.com/stadium_pictures/asia/north_korea/pyongyang_may_day.shtml