The Adamantine Tower is believed to be one of the oldest buildings in Tamriel, if not the entirety of Nirn.  It is believed to have been built by the Aedra soon after the creation of Mundus, around ME 2500.  The structure later became known as Direnni Tower, and is located on the Isle of Balfiera.
It is said that the building of Adamantine Tower ended the Dawn Era and signalled the start of the Merethic Era , as stated here: 'The Dawn Era ends with the exodus of the gods and magic from the World at the founding of the Adamantine Tower.
It has been suggested that Lorkhan was unmade by the Gods at this tower . There are numerous explanations as to how this was done . What is known as that the process of unmaking the god, a byproduct of which was the Heart of Lorkhan was known as the War of Manifest Metaphors.  This war made it impossible to accurately define the events that took place during the unmaking,  similar to the reasons for which Elder Scrolls cannot be explained fully.
Sometime after the events at the beginning of the Merethic Era, the Direnni Clan decided to use the tower located in the Isle of Balfiera. Many Dirennis were famous , and the clan has lived in this tower for many centuries . Later, it was renamed to Direnni Tower, in honor of the clan 
- ↑ Pocket Guide to the Empire, Third Edition: High Rock
- ↑ 2.0 2.1 2.2 Before the Ages of Man
- ↑ Pocket Guide to the Empire, First Edition: High Rock
- ↑ Mysterious Akavir
- ↑ 5.0 5.1 Pocket Guide to the Empire, Third Edition: Eras
- ↑ 6.0 6.1 6.2 The Lunar Lorkhan
- ↑ The Elder Scrolls III: Morrowind
- ↑ 8.0 8.1 8.2 Du Rerum Dirennis
- ↑ The Elder Scrolls II: Daggerfall