Thilla is a rare example of a well-preserved Yemeni highland town of local stone houses and paved streets surrounded by a massive stone perimeter wall. Sited at the foot of a high mountain, the inhabitants of this ancient town took refuge in a fortress on the mountaintop in times of conflict. This old building displays fine stonework, arched windows and beautiful plasterwork friezes. Note the coloured-glass windows, which are a feature of so many Yemeni homes. In years gone by, dyed translucent alabaster was used instead of glass.