A corridor on the Rupadhatu layer of the Borobudur Temple
The Borobudur Temple has three distinct layers, each of which reflect the Buddhist concept of a realm that a human being needs to go through to attain enlightenment. These realms are: Arupadhatu, Rupadhatu and Kamadhatu. Representing Arupadhatu is the top layer comprising of three round terraces. Representing Rupadhatu is the middle layer comprising of five square terraces. Representing Kamadhatu is the lower layer, which is the terrace at the courtyard level.
The image shows a corridor of one of the terraces of the Rupadhatu layer.