Ink and pencil
Here, you can see contradicton between top and bottom of the artwork. At the bottom we see outer corner of the castle wall, but at the top it transforms into inner corner.
Artist used such Escher's motifs as large detailed painted plants and interacting people in impossible construction.
Artist's website http://www.csilverman.com
Outside Up (1998)
The image was found at http://www.csilverman.com/gallery/surreal/outside-up/