How many venues are located at Centurion, South Africa?
venues are located at Centurion refers to city_name = 'Centurion'; South Africa refers to country_name = 'South Africa'
SELECT COUNT(T1.Venue_name) FROM Venue AS T1 INNER JOIN City AS T2 ON T1.City_Id = T2.City_Id INNER JOIN Country AS T3 ON T2.Country_Id = T3.Country_Id WHERE T3.country_name = 'South Africa' AND T2.city_name = 'Centurion'