The temple was started in 98AD, the first year of the reign of Emperor Trajan, according to dendrochronological analysis of the numerous oak posts that support the walls. It appears that the temple wasn't part of the original plan of Aventicum and so it may have been added under the direction of Trajan. Trajan had served with the Roman army along the Rhine, and after his ascension to the throne may have had the temple built to represent his power over the northern reaches of the Empire.