This is a jai-alai square built in 1904 to play pelota by architect Eusebio Madariaga for businessman Francisco Irusta. It was completely reformed in 1969 by architect Castor Uriarte. It is interesting because it held games in which people betted on who was going to win but also all sort of social activities: political meetings (Spain’s Socialist Party PSOE’s first meeting after democracy was brought back in 1976), meals, concerts, cockfights, dances, boxing matches. Even the proclamation of the Spanish Republic in 1931 was held here. Its name comes from Basque Monday, as it was the day of the week in which more games were played. Notice its modernist traces, such as the window over the main door.