Community Nucleus (Arena) strategy

Nucleus (Arena) strategy.

General

Heavies and Soldiers should be alert of enemy Snipers. Going into the doorway near the spawn is a good way to avoid them.
The circular nature of the map allows for easy access to the opposing team's spawn entrance, which in turn opens for ambushing.
The roof on one side of the map has an opening on the top, giving Soldiers and Demomen an opportunity to do much damage without being noticed.

Scouts with the Force-A-Nature and Pyros with either the Flamethrower or the Degreaser equipped can use their weapons to knock their opponents into the center pit and to an instant death. This also works for Soldiers and Demomen, although this is more difficult.
There are many fast routes in the map that are ideal for Scouts. Jumping over the chasm can provide a quick escape from an enemy. The medium health pickup is only two jumps away from almost any point on the map, seeing as it's placed low and in the middle.
At the start of a round, Scouts are able to jump on the roof of a low building to the right or to the left as they leave spawn depending on which team you are on (BLU = Left, RED = Right). This allows access to a fast route to the other team's spawn area. Be advised that Soldiers and Demomen may favour this route as well.
It is possible, albeit highly difficult, to escape from the lower platform of the map to the surrounding ledges as a Scout by double jumping and crouching as you approach the edge of the ledges. This technique is made much simpler through use the Force-A-Nature, though it can be performed by any Scout, regardless of loadout.

As a Pyro, Try to stay around the Health Pack and airblast any enemies going for it into the pit, This is very effective against damaged enemies.

Stickybombs are very effective when placed on the Health Pack, As they will kill damaged enemies going for it.

This map allows for successful Heavy ambushes, as the narrow catwalks leading to the center Control Point give enemies no space to avoid the Minigun.

As the Engineer, you can deploy a Sentry Gun near the medkit, which finishes off any enemies with low health trying to get to the medkit.
Sentry Guns are extremely effective when used in the Flank Building.

At the start of a round, run out of Spawn and go to the right, You should have a good position to Headshot any enemies running for the stairs.
A good Sniper position is on the second floor of the access building, As there is good view of the map.

Though overall a good map for Spies, the circular nature of the map disrupts line of sight, meaning you have little warning before enemies are suddenly upon you.