Roman camps followed a standard pattern for defense and religious ritual; in effect they were Rome in miniature. The commander's headquarters stood at the centre; he took the auspices on a dais in front. A small building behind housed the legionary standards, the divine images used in religious rites and in the Imperial era, the image of the ruling emperor. In one camp, this shrine is even called Capitolium. The most important camp-offering appears to have been the suovetaurilia performed before a major, set battle. A ram, a boar and a bull were ritually garlanded, led around the outer perimeter of the camp (a lustratio exercitus) and in through a gate, then sacrificed: Trajan's column shows three such events from his Dacian wars. The perimeter procession and sacrifice suggest the entire camp as a divine templum; all within are purified and protected.