Claim from http://iMapp.ro:
The artistic works of the participating teams will be displayed on the largest projection surface in the world – the facade of the Palace of of Parliament (23,000 square meters)
I witnessed the event yesterday and it certainly was a massive experience to behold, but one would imagine there are easily larger surfaces that could be used for projection mapping, such as Mt. Rushmore or Half Dome.
The facade of the Palace of the Parliament has been used as a projection mapping surface since 2014, if not earlier.
Might the Palace be the largest artificial surface that has been used for projection mapping, as of September 2021?