Indeed, a Tower is defined by its function, not by its appearance.

edit:

As for Alduins wall, I only see the events of Morrowind represented by Akhulakhan and Oblivion as the Tower ontop of an Oblivion gate. Where do you see the events of Arena?.

I had to look that one up. It's covered up by a cobweb ingame, but through the website viewing of Alduin's Wall, there's a staff broken into 8 pieces.

It wasn't on the wall shown in the demo materials, which annoyed me to no end. It is on http://www.gameinformer.com/p/skyrim_wall.aspx, though. There's the Staff for Arena, the Numidium for Daggerfall, Red Mountain for Morrowind, and the Oblivion Gate for Oblivion.

That doesn't mean that the Staff is a tower or even a symbol of any import. The wall is a prophesy, saying "after the staff breaks" rather than "because the staff breaks."

Thanks and damn. I've been looking at the http://www.imperial-library.info/sites/default/files/gallery_files/skyrim_teaser_wall_0.jpg and it's impossible to make out those details.

I quite agree. There is nothing that states that these events cause Alduin’s return, this is pure speculation on my part (a more likely conclusion might be that Bethesda were simply creating a continuity between their games).

My reasoning in part is based on the ‘solutions’ to at least Morrowind and Oblivion main quests involving actions that lead to negative consequences in the following episode: Removal of the Heart weakens the limnal barriers, defeating Dagon also ends the Septim dynasty and so weakens the empire.

Daggerfall, Morrowind and Oblivion involve the destruction of Towers that variously relate to the stability of Mundus (Numidium perhaps less so in itself but a regional Dragon Break is no small matter). Skyrim’s civil war feeds Alduin.

So if these events are the foundations of the kalpa’s doom rather than omens to be witnessed then the Staff seems out of place. The chronology is also strange: Four portents within 40 years of each other and the last 200 years later with no mention of a Great War or missing moons in between.

My conjecture upon conjecture therefore is that if Staff is the Tower the Selective broke the Dragon with then dismantling it would also affect Mundus’ stability. The culmination of all of these events enables Alduin to consume the kalpa.

My other angle is that there are two instances of an eight-piece-kit staff one (Tharn’s) that is regarded as being of great power but only seems to do things that a reasonably adept mage could do and the other (the Selective’s) that clearly is very powerful but of unknown origin and location post Break.

The UESP article on the Staff of Chaos describes it as: “Having been forged from the essence of the very Land itself” I’m not submitting that as part of my argument however as I can’t find the source for that statement. I include it in the hope that someone might know what, if anything, it’s based on.

They may not cause it directly but they are all part of the prophecy as N stated. From the Book of the Dragonborn:

When misrule takes its place at the eight corners of the world
When the Brass Tower walks and Time is reshaped
When the thrice-blessed fail and the Red Tower trembles
When the Dragonborn Ruler loses his throne, and the White Tower falls
When the Snow Tower lies sundered, kingless, bleeding
The World-Eater wakes, and the Wheel turns upon the Last Dragonborn.

The Dragonguard shouldn't have hired Tsaesci labor unions to build Alduin's Wall. It took too long and the results were meh. The Dragonguard should have known better after the union's shoddy workmanship caused the dracostatic shipping wareHouse of Padhome strike of 1E 105. So many delayed shipping orders...