Full list of all 16 Monument Valley 2: Panoramic Edition achievements. It takes around 1-2 hours to unlock all of the achievements on Windows.
Looks like you found an Easter Egg
Completed Mirador
Completed The Sunken City
Completed The Orchard
Completed The Lyceum
Completed The Botanical Gardens
Completed Lost Forest
Completed Mén-An-Tol
Completed Aphelion
Completed The Towers
Completed The Docks
Completed The Archipelago
Completed The Viaduct
Completed The Oasis
Completed The Vestibule
Completed Prelude