Nursery plants are seen placed in people's seats during a rehearsal as Barcelona's Gran Teatre del Liceu opera reopens its doors with a concert for plants to raise awareness about the importance of an audience after the lockdown, amid the coronavirus disease (COVID-19) outbreak, in Barcelona, Spain June 22, 2020. Barcelona's Liceu opera house reopened its doors on Monday for the first time in over three months. REUTERS/Nacho Doce

Nursery plants are seen placed in people's seats during a rehearsal as Barcelona's Gran Teatre del Liceu opera reopens its doors with a concert for plants to raise awareness about the importance of an audience after the lockdown, amid the coronavirus disease (COVID-19) outbreak, in Barcelona, Spain June 22, 2020. REUTERS/Nacho Doceconc

Nursery plants are seen placed in people's seats during a rehearsal as Barcelona's Gran Teatre del Liceu opera reopens its doors with a concert for plants to raise awareness about the importance of an audience after the lockdown, amid the coronavirus disease (COVID-19) outbreak, in Barcelona, Spain June 22, 2020. REUTERS/Nacho Doce

Nursery plants are seen placed in people's seats during a rehearsal as Barcelona's Gran Teatre del Liceu opera reopens its doors with a concert for plants to raise awareness about the importance of an audience after the lockdown, amid the coronavirus disease (COVID-19) outbreak, in Barcelona, Spain June 22, 2020. REUTERS/Nacho Doce

Nursery plants are seen placed in people's seats during a rehearsal as Barcelona's Gran Teatre del Liceu opera reopens its doors with a concert for plants to raise awareness about the importance of an audience after the lockdown, amid the coronavirus disease (COVID-19) outbreak, in Barcelona, Spain June 22, 2020. REUTERS/Nacho Doce

Nursery plants are seen placed in people's seats during a rehearsal as Barcelona's Gran Teatre del Liceu opera reopens its doors with a concert for plants to raise awareness about the importance of an audience after the lockdown, amid the coronavirus disease (COVID-19) outbreak, in Barcelona, Spain June 22, 2020. REUTERS/Nacho Doce