London (KSDK) -- One of the most popular sport for spectators is Olympic pin trading.
People from around the world gather in Olympic Park for the must-have souvenir.
Olympic pins date all the way to the first modern games in Athens in 1986 when small cardboard discs were first used to identify athletes and judges.
The use of metal badges started with the St. Louis Olympics in 1904.
Some collectors have more than 20,000 pins.