St John on Patmos is the more significant artwork and was placed in the interior, with The Eye of God with Scenes from the Passion. Tondo are circular paintings and were frequent throughout the Renaissance, though far less frequently seen now. Perhaps Michelangelo created the most famous of all, with Doni Tondo.
The interior scene captures St John witnessing the Revelation, with all the symbolism that you might expect included around this beautiful painting. For instance, the devil is present and attempting to disrupt the story in line with a story commonly taught in Bosch's region of Europe during that time.
There is also another opportunity to enjoy Bosch's skills within landscape painting, always used as a backdrop rather than the main focus. It was later with the likes of Turner and Constable that landscapes would take all of the limelight for the first time.
The landscape backdrop has more detail than in most of his other paintings, taking the time to incorporate fields, buildings, and a vast river that drifts across the scene. It would be good enough by itself as a landscape painting in its own right, even before he added the religious themes and figurative portraiture.
This original work was part of a private collection in London before being sold on to the public Berlin Museums in 1907, where it has remained ever since as part of several permanent displays. It is also believed to have been the first artwork with Bosch's trademark signature.
The exterior is a darker, more subdued painting that depicts the all-seeing eye of God as if a threat to all those who follow the wrong path. Outside of his eye is pure darkness and this symbolic work represents the importance of following the right moral direction in your life.