Complex sentence: South of the latter was a slope consisting of sand and gravel, deliberately left unbuilt for defensive purposes, and, probably extending further south than the present, leading to the royal stables and gardens and the butchers stalls on the opposite side.
Split into simpler sentences: South of the latter was a slope consisting of sand and gravel, deliberately left unbuilt for defensive purposes. Probably wider than the present slope, it stretched south to the royal stables and gardens and the butchers stalls on the opposite side.