Gaining Political Backing
With a site found and secured, the magi must now turn to their peers and gain sanction for, or at least acceptance of, their plans. The building of the Great Tower is not something that can be done in isolation and without word of it reaching the Order. There must be some kind of accord or else the project is doomed to

failure before it even starts.
This may be easier in some Tribunals than others. The Tribunal of the Greater Alps is tightly controlled by centuries of tradition, and the magi there are unlikely to accept any new magi who cannot prove that they can support themselves. While it may easier to found a new covenant in Normandy, especially with the support of powerful patrons, the lands of France are the heartland of Mythic Europe. Mundane power rules supreme and a tower the size of a town or city may not be tolerated by the magi of Normandy, for fear of provoking the mundane nobles they share the land with.
The Tribunal of Rome poses different challenges. While magi typically find it easy to establish covenants there, they do so in an unofficial capacity. They find themselves tolerated by the existing covenants so long as they offer no challenge to the convoluted status quo of both open and insidious conflict that reigns there. And magi seeking to build the Great Tower in Iberia will quickly find themselves pressured by both Christian and Moorish nobles to support one side or the other in controlling the peninsula.
The Tribunals of Stonehenge, Loch Leglean, and Hibernia still hold both ancient magic and remote wilderness. The more distant reaches of these places may hold the key, especially if the Great Tower can be seen as a way to draw those Tribunals towards the center of Hermetic politics and influence. The same can also be said of the more distant reaches of the Order, such as Novgorod or the Levant, especially if the tower can be used to either secure new unclaimed land or to wrest it away from their Hermetic neighbors.