Bath city walls the Romans, to surround their town (known then as "Aquae Sulis"), probably in the 3rd century. The Anglo-Saxons by the 10th century had established Bath as a fortified "burh" (borough), utilising the existing town walls, and maintaining Bath as a centre of regional power. Bath, located on the northern edge of the kingdom of Wessex, would have guarded against any attack from neighbouring Mercia, which was held by the Danes for a time. The height of the walls was increased on the orders of King Stephen during The Anarchy. Bath's medieval walls included four gates. The North and South Gates
Aphanizomenon flos-aquae (dietary supplement) and sun exposure can greatly affect lipid and pigment composition. As more is learned about the components of different cyanobacterial species, growers and harvesters are better able to determine the optimal growth conditions for obtaining optimal yields. " Aphanizomenon flos-aquae" has been shown to contain varying amounts at least 13 vitamins: vitamin A (beta-carotene), vitamin C (ascorbic acid), vitamin E, vitamin K, and many of the B-complex vitamins including B (thiamin), B (riboflavin), B (pyridoxine), choline, biotin, niacin, folic acid, pantothenic acid, and B (cobalamin). However, "Aphanizomenon flos-aquae" contains pseudovitamin B which can block absorbtion of true B and is