Regular Division of the Plane Regular Division of the Plane Regular Division of the Plane is a series of drawings by the Dutch artist M. C. Escher which began in 1936. These images are based on the principle of tessellation, irregular shapes or combinations of shapes that interlock completely to cover a surface or plane. The inspiration for these works began in 1936 with a visit to the Alhambra, a fourteenth-century Moorish castle near Granada, Spain. Escher had visited the Alhambra once before in 1922 but in this visit he had spent several days studying and sketching the ornate tile designs there. In 1958 Escher
Moorish Gibraltar the western and southern flanks, with towers and connecting passages added to strengthen them. The existing fortifications were also strengthened and repaired. The weak points that the Castilians had exploited were improved. The refortified city – the final incarnation of Moorish Gibraltar – stood in the north-eastern part of the present-day city, reaching from the area of Grand Casemates Square up to Upper Castle Road. It was divided into three main quarters. At the top was the Tower of Homage (just part of the Moorish Castle but usually referred to as such), a formidable square keep situated within a kasbah.