Jericho

This is a Muslim Six pointed Star from the eighth century C.E. in Hisham palace (Khirbet El-Mafjar) located 3 km north of Jericho. 

Picture is courtesy of "markuscuel" who published it on Flickr. 

This is not the only hexagram in Hisham's Palace:

a. K.A.C Creswell shows in his book (Early Muslim Architecture, Vo. I part 2, Oxford, 1969 p. 558) a window-grille reconstructed from fragments which had been printed red or brownish-gold, drawn on equilateral triangles network. There are several hexagrams and a six petaled rose in each of them.
b. In p.572 there's another photo of a grill from diwan of bath dated to 739-43 C.E.