The major sight of interest at the archaeological site of Bulla Regia - first a Numidian then a Roman settlement and undoubtedly inhabited until the Middle Ages - is the complex of extremely well-preserved patrician houses, in which the underground living quarters are illuminated via a central courtyard. Even today, two conflicting hypotheses attempt to explain the layout of these buildings: a desire for cool conditions in a region where temperatures can exceed 40°C; or the need for additional living space in a highly concentrated urban area. Whatever the reason, a visit here is hugely interesting.