A sign that reminds visitors of keeping distance is seen in Kunsthistorisches museum in Vienna, Austria, May 30, 2020. As one of the most famous museums in the world, Kunsthistorisches museum reopened on Saturday after a lockdown. Visitors are required to wear masks and keep distance when visiting the museum. (Photo by Georges Schneider/Xinhua)

Visitors visit the Kunsthistorisches museum in Vienna, Austria, May 30, 2020. As one of the most famous museums in the world, Kunsthistorisches museum reopened on Saturday after a lockdown. Visitors are required to wear masks and keep distance when visiting the museum. (Photo by Georges Schneider/Xinhua)

Visitors visit the Kunsthistorisches museum in Vienna, Austria, May 30, 2020. As one of the most famous museums in the world, Kunsthistorisches museum reopened on Saturday after a lockdown. Visitors are required to wear masks and keep distance when visiting the museum. (Photo by Georges Schneider/Xinhua)

Visitors visit the Kunsthistorisches museum in Vienna, Austria, May 30, 2020. As one of the most famous museums in the world, Kunsthistorisches museum reopened on Saturday after a lockdown. Visitors are required to wear masks and keep distance when visiting the museum. (Photo by Georges Schneider/Xinhua)