Conventionally in an investigation of comparing various locations, we would look at printed materials and play a game of "spot the difference". With one of ArcGIS Online's applications, it opens up new methods to investigate maps.
Auckland aerials from 1940 to 2016
Through the use of Auckland Council REST Services, we can create web applications (Web App) to show a series of historic aerials from 1940 to present. This allows users to identify and detect changes of landscape throughout time (such as landuse / landcover change).
Now and Then | Christchurch CBD Revealed
The spyglass effect fits perfectly with investigating historic area of interest in an interactive approach. The example below powered by ESRI Australia illustrates the application of revealing history below the "surface" of Christchuch CBD.