Millwall are renowned for having one of the most passionate supporter-bases in the EFL.
Fans of the Lions love nothing more than getting behind their team at the The Den and making life hard for their opponents as they look to come away from South Bermondsey with all three points.
Millwall moved to their new stadium in 1993 and have certainly managed to turn it into a fortress as they look to fill all 20,146 seat in attendance.
But does The Den have a higher or lower capacity than these 18 grounds? Have a go of our quiz and test yourself!