velarium
The marginal membrane of certain medusae belonging to the Discophora.
An awning that stretched over the seating area of the Colosseum in Ancient Rome and other Roman amphitheaters.
historical
A cloth stretched over another space, such as that stretched below the roof of the Royal Albert Hall.
In accordance with the epochal significance of the occasion, Berlin was decked out as never before in its history. […] A velarium suspended over Unter den Linden depicted the great military victories that had finally brought Germany its unity.
Where it comes from
From Latin vēlārium, from vēlum + -ārium. Doublet of veghar.
Adapted from the Wiktionary entry velarium (CC BY-SA 4.0).