Citadel Tower
From Mass Effect Wiki
The Citadel Tower is at the epicenter of the massive Citadel. Rising parallel to the station's Wards, the Tower is the most distinctive monument on the Citadel and is home to the Council. From here all Council decisions are made, decisions that shape the galaxy and the beings within its space.
The Tower is home to the Council Chambers, which are full of cherry trees and beautiful fountains. Sets of stairs in the anterooms lead up to the Council's audience chamber. In Mass Effect: Revelation this area was called the Petitioner's Stage. Beneath the stage is a garden protected by glass. There are many people in the Chambers, either politicians or individuals trying to petition the Council (like Rear Admiral Kahoku). Commander Shepard can listen in to conversations between a salarian and a turian about the rumours of Saren Arterius' involvement in Eden Prime, and about the chances of the volus getting a Council seat (next to none according to the salarian).
According to Avina, the keepers make frequent appearances in the Tower and the Council Chambers, though they just seem to be passing through on their way somewhere else.
The Citadel Tower is accessed either from an elevator on the Presidium, near the Relay Monument, or from any Citadel Rapid Transit location.
If Wrex is in the shore party and talked to, he'll remark that there is not mush visible security in the tower. "Ten to one, there's a sniper watching our every step." On another note, Ashley will observe that the plentiful staircases "make for good defensive positions if this places is ever attacked."
The Tower is not merely an edifice, it is somehow used to manually open the Citadel Relay leading to dark space. When Sovereign attacked the station, it settled on the Tower and extruded cables into it.
The Council Chambers were the scene of the final battle between Shepard and Saren during the Citadel incursion. Pursuing Saren to the station's master control unit, which turned out to be in the Council's audience chamber, Shepard saw Saren die and fall through the glass into the garden below. Saren's transformation into Sovereign's 'avatar' caused the stage to collapse and the squad battled the creature in the garden until it was finally destroyed.
When Sovereign was blown up by the Alliance and what remained of the Citadel Fleet, a large piece of debris crashed straight into the Tower. Shepard's team was almost buried by rubble and the commander was nearly crushed under it, but they were found by a rescue team led by Captain Anderson.
