Purchase a ticket and join the crowds at a game at Johannesburg Stadium. If there's nothing on while you're there, you might like to check if the stadium offers a tour of the grounds.
You'll have to pay an entry fee, so bring some money and get ready for a fun day out. But Johannesburg Stadium isn't the only thing to visit in the commercial district of Downtown Johannesburg. You'll find other worthwhile attractions such as Gold Reef City, Sandton City Mall and Apartheid Museum close to the sporting facility.