Madrid's bullring is the biggest i n Spain ... About 22,000 person capacity ( always full during the May festivities ) . Bilbao's bullring is very different as the ring itself has a special surface to deal with the amount of rain the País Vasco gets . The bullring there is just about a 15 minute walk over the river from the cathedral in a semi-residential area . When you're in Bilbao you should walk through the little old streets in the Casco Viejo ... If you're lucky you may walk down a street and hear the sound of what seems a bit like tennis .. I was lucky and was walking down a narrow lane just a little North of the Casco Viejo .. Lots of old guys in their black berets ( Boinas ) and young guys were crammed into the doorway of an old sports centre where you can go in for free and watch the Basque game of Pelota Vasca .. In which they use a large wicker 'basket' attached to their hand or , as I saw , just their hands to slam balls at high speed against a back wall .. a bit like squash . It's very fast and dangerous .
Also do not miss a ride across the river to or from Getxo on the Puente Colgante .. a cable car that hangs down from a huge bridge structure a few metres above the river .Getxo is a very wealthy area of Bilbao that has seen it's fair share of bombings by the terrorist group ETA . My Basque friend took me there for the ride and for the great restaurants/bars .
And as a footnote to your message .. I know that MM is a HUGE fan of football .. Many a time I met him for lunch after he'd been up all night watching a game .