The Atlantis of the Sands is the twenty-first chapter in Uncharted 3: Drake's Deception.
After arriving in Ubar, Drake and Sully begin to explore the city. They stumble upon a water fountain that Drake drinks out of, amazed that water system still works. However, the two notice a solar eclipse, and suddenly Sully is shot dead by Talbot. Nate, overcome with rage, chases after Marlowe and Talbot but first he must confront Marlowe's agents who appear to have been possessed by the spirits of the Djinn. They will hurl explosive fireballs at Nate that can cause serious damage. Once defeating them, ride down the elevator Marlowe and Talbot went down in. After descending, chase after Talbot who will then disappear around a corner.
Nate then mysteriously transports to Cartagena, Colombia and a swarm of spiders chase him through the city. Run down the street and jump across the rooftops to escape. Nate ends up cornered on the rooftop where he was saved by Sully when he was a kid, but Sully is the one pointing the gun at him instead of an agent. Either shooting Sully when prompted to or waiting until Sully shoots Nate will make Drake reawaken back in Iram of the Pillars, where Nate will encounter more Djinn who arrive down the elevator.
After taking out the Djinn in the elevator and a courtyard, Nate sees Sully in a room up ahead but he disappears behind a closed door. In order for it to open, Nate must push down on a lever that will fill the pool up with water. Nate's reflection will move on its own to help him turn the wheels to open the door. A bright light appears in the pool of water and Nate examines it, only to be thrown through the roof by his reflection. Nate reawakens in the same room, now with dead bodies of the people who lived in the city.
He exits the room and heads downstairs to the underground water system where Marlowe and Talbot are.
I. Head through the doors, using a quick diversion to acquire Treasure #94 when the main staircase branches into 2 paths, then head down the steps on the right. Collect Treasure #95 when you reach a break in the balustrade to your left. At the bottom, approach the fountain to trigger a momentous cinematic.
II. When the action resumes, take cover behind the barriers to your left. Engage the hostiles to the east first. You will soon notice that something is amiss when headshots are rendered useless; see the "Fire Spirits" article for advice on this new opposition force. There are initially 3 to battle in this area. You can find an RPG-7 and a Tau sniper inside the tower to your east (where the first Djinn is stationed), with an M-32 Hammer partially concealed in foliage at the top of the stairs leading out from the far side of this structure. These are nigh-essential to defeat these foes in a timely manner, unless you have specifically brought suitable weapons from the battle outside the city. After they have been defeated, reinforcements will arrive via the elevator. Try to greet these with an explosive barrage if possible, or at the very least a simple grenade blast. If you are killed in the second part of this battle, note that the grenade and rocket launchers will reappear in their original positions. Once the battle has ended, collect ammunition and acquire Treasure #96 before entering the elevator. Step on the button at the centre to ride it down.
III. This section of gameplay is more an experience than a challenge, so stop reading this entry NOW if you would prefer to take it in for yourself without prior warning. Pursue Talbot through the streets. Once you reach the dead end, go along the familiar road until a surprising danger appears. Run into the screen to escape. After bursting through the doors, make your way over the rooftop assault course; though certain camera angles are different, refer to Chapter 3: Second Story Work if you need to refresh your memory on specific jumps or directions.
IV. Back at the elevator, collect Treasure #97, and sprint into the street ahead. Interact with the gate at the end to trigger the arrival of 3 Djinn. From your starting position, use M-32 Hammer rounds (there's one just to the left of the first cover position, as well as a Tau Sniper) to defeat the shotgunner first, then turn your attention to the pair that remains. You can now head through the gate to face two further Fire Spirits. Toss a grenade between them as you enter to weaken both, then concentrate on a single target at a time with the Tau.
V. Head up the steps to enter a new area and immediately sprint to the left, taking cover behind the pillar in the corner. Grab the Tau and RPG-7, then target the shotgunner Shade zeroing in on you. Once he has been dispatched, you can find a T-Bolt Sniper, a new Tau Sniper and an M32-Hammer positioned on the outer edge of this area. Using the pillars and pool walls as cover, stay mobile as you engage enemies, never lingering in any one area long enough for them to consolidate and flank you. When the battle end, collect weapons (the G-MAL being highly recommended) and head through the new doorway.
VI. When Nate is locked inside the room, run over to the lever at the far side of the empty pool and press triangle to operate it. This begins a short and simple puzzle. If you would like to attempt to solve it yourself, stop reading NOW. Watch the reflection in the water, and see the ghastly Nate go to the pool's left side. Follow him to the inside of the wheel 'above' his position and press triangle to operate it, then follow him again to the opposite side and repeat the process. Run into the pool's centre and press triangle, then tap the button rapidly when prompted. When Nate comes to his senses, leave via the sole exit and collect Treasure #98 from the corridor. Sprint down the spiral staircase to reach the final chapter.