Athletic Bilbao B
Bilbao Athletic, officially named Athletic Club "B", is the reserve team of Athletic Bilbao, a football club based in Bilbao, in the autonomous community of Basque Country. The team will play in the Segunda División B in the 2018–19 season. Founded in 1964, the team holds home matches at the small stadium attached to the club's training facility at Lezama, or occasionally at San Mamés Stadium, with its 53,500-seat capacity, for important fixtures.
Atlético Madrid
Athletic's first ground, the Ronda de Vallecas, was in the eponymous working-class area on the south side of the city. In 1919, the Compañía Urbanizadora Metropolitana—the company that ran the underground communication system in Madrid—acquired some land, near the Ciudad Universitaria. In 1921, Athletic Madrid became independent of parent-club Athletic Bilbao and moved into a 35,800-seater stadium built by the company, the Estadio Metropolitano de Madrid. The Metropolitano was used until 1966, when they moved to the new Estadio Vicente Calderón. After the move, the Metropolitano was demolished and was replaced with university buildings and an office block belonging to the company ENUSA.