Atlantis is an Arena map introduced in the 8.0.0 update.
It looks like Atlantis, except that the player is inside a glass room with golden details and a giant light bulb with 4 golden pillars with pink tiles in the title. Also one of the background buildings have "PIXEL GUN" on them.
There are many strategies to play Arena Mode in. An effective strategy is to have a Signal Pistol, which is basically made for this mode as it takes out mobs of enemies in max 3 hits with the end mobs 2 with the mix 1 with the regular.
Always aim for the weak-points (like the head) in order to deal extra damage. This tip will lead into a shorter battle and ameliorated ammunition conservation.
Another great strategy is with a Primary weapon. Use them and aim at the head is possible. Also, try to keep on having good armor and to run around in a circle around the arena while shooting at the enemies. This will allow for a large score, while getting lots of coins.
Always manage your ammunition. Some weapons like the Old Revolver can easily run out of ammunition, so try collecting as many ammunition pick-ups as possible. Picking them up will not only make your Old Revolver receive more ammo, but all of your equipped guns will receive an extra clip. Also, try burst firing, especially with weapons that can easily run out of ammunition.
Always manage your health and armor, as you only have one row of health and armor each.
The best maps that you can play in are any map except Ice Hockey Arena and Scary Pizzeria. In Ice Hockey Arena, you will have difficulties walking on the floor, due to the slippery ice on the floor. In Scary Pizzeria, there are too many walls for an arena-based map, which may give you difficulties running around the map.
Using Your Own Loadout
There are many strategies to play Arena Mode in. An effective strategy is to have an explosive weapon with decent mobility like the Anti-Gravity Blaster which is basically made for this mode as it takes out MOBS of enemies in max 3 hits with the end mobs 2 with the mix 1 with the regular.
A Dark Matter Generator also works with this role as it has similar if not identical properties as the Anti-Gravity Blaster. Once you picked your weapon, its time to roll. When you are out you should keep collecting ammo for your Gravity gun/Bass cannon and also keep collecting shields. when you reach wave 10 a good tactic is to jump on the heads of mobs via rocket jump to then rocket jump of their heads killing them in fours and fives.
Another great strategy is with the Automatic Peacemaker, or any kind of minigun related weapon. Due to the amount of bullets the peacemaker has, the player can go at least for about 30 or more rounds without dying if the player has good armor, keeps collecting ammo pickups, and runs around in a circle around the arena while shooting at the enemies. This will allow for a large score, while getting lots of coins.
A good throw of a Throwing gadget into a crowd wears their health out, making them easy to pick off. And the Singular Grenade groups mobs into one area, making them more vulnerable to crowd-control weaponry, including the Ghost Lantern. As the lantern kills most mobs nearly with a shot. However, you need to watch out if there are any ranged enemies in the black hole, because they can still attack you.
Pets can help you locate remaining enemies if you have trouble finding them.
Also, the Storm Hammer and the Fire Orb helps a lot in this mode, as its good for crowd control and requires no ammo to swing around, but, watch out for ranged enemies and take them out similar of how you kill a ranged player with those melee weapons.
Using the Christmas Tree Turret will make the enemies go against it, making them prioritizing on attacking it before they attack you.
As in the original Atlantis map, a pink neon sign that vertically says "PIXEL GUN" can be seen.
Since most of the arena is glass and water is see-through, players can see what lies behind the doors where the enemies come from. One hallway leads inside a hill, another goes to an elevator room (which supposedly goes to the surface), another goes a room where a chandelier is seen inside due to the glass, and the last one leads to a room that has a solid wall, obstructing view of the inside.
One part of the room has leaking water from the roof.