Who says you always have to battle in the same, old stadium? With a little holographic tech, we can alter the Colosseum environment to suit a wide range of tastes. Basically, different arenas will have four changes: The natural weather, Camouflage, Nature Power, and Secret Power.

Weather is pretty obvious. None (standard), Rain, Sunny, Sandstorm, Hail, or Shadow Sky (from Pokemon XD)

Camouflage is a fairly rare move, but I'm trying to come up with a way of making it more widely-available. Basically, it changes the user's type to something appropriate to the battlefield.

Nature Power draws on the environment to produce a different attack. For example, battling on sandy ground will cause Nature Power to become Earthquake.

Secret Power is a Normal-type attack with 70 base power and a 30% chance of causing a side-effect. The effect is different based on the terrain.

So now I present to you the arenas and what they do!

Default Colosseum
Innate weather - none; Camo - Normal
Nature Power - Tri Attack; Secret Power - Paralyze foe

Thard
These are my personal creations

Blackmoon Colosseum
(All Data Top Secret!)
No one has fought here yet so I'm keeping it under wraps.

Crystal Spring Colosseum
Innate weather - none; Camo - Normal
Nature Power - Recover; Secret Power - User's Sp.Def up

Stormbound Colosseum
Innate weather - Hail; Camo - Ice
Nature Power - Thunder; Secret Power - Foe's Accuracy down

Iron Fist Colosseum
Innate weather - none; Camo - Steel
Nature Power - Iron Defense; Secret Power - Foe will Flinch

Lover's Field Colosseum
Innate weather - none; Camo - Grass
Nature Power - Attract; Secret Power - Foe goes to Sleep

Disco Fever Colosseum
Innate weather - none; Camo - Normal
Nature Power - Rapid Spin; Secret Power - Foe's Attack down

Pacific Northwest Colosseum
Innate weather - Rain; Camo - Water
Nature Power - Water Pulse; Secret Power - Foe's Speed down

Pharoh's Colosseum
Innate weather - Sandstorm; Camo - Rock
Nature Power - Rock Tomb; Secret Power - Paralyze foe

Nine Circles Colosseum
Innate weather - Sunny; Camo - Fire
Nature Power - Heat Wave; Secret Power - Foe is Badly Poisoned (Toxic)

Surfside Colosseum
Innate Weather - None; Camo - Ground
Nature Power - Water Sport; Secret Power - Foe is Burned

Starstorm Colosseum
Innate weather - Shadow Sky; Camo - Shadow
Nature Power - Shadow End; Secret Power - Drain HP (100% of damage dealt)
Shadow End: 120 power, 60 acc, user loses 1/2 current HP as recoil

Spear Pillar Colosseum
Innate weather - None; Camo - Dragon
Nature Power - Draco Meteor; Secret Power - User's Speed up

Torn World Colosseum
Innate weather - Trick Room; Camo - Ghost
Nature Power - Curse; Secret Power - Confuse foe

Panaramic Penguin
A former Aquan, inspired by my arenas, decided to create some more. This isn't his complete list, just the ones I thought would be most interesting. They're all based on various video games.

1. Aqua HQ (Pokémon Ruby & Sapphire)
Innate weather - Rain; Camo - Water
Nature Power - Surf; Secret Power - User's Attack up

2. Orre Colloseum (Pokémon Colloseum)
Innate weather - Sandstorm; Camo - Rock
Nature Power - Earthquake; Secret Power - User's Evasiveness up

3. Sliph Co. (Pokémon Red & Blue)
Innate weather - None; Camo - Psychic
Nature Power - Psywave; Secret Power - Confuse foe

7.Shiver City (Paper Mario)
Innate weather - Hail; Camo - Ice
Nature Power - Powder Snow; Secret Power - Freeze foe

8.Talm Ruins (Legend of Zelda: Oracle of Seasons)
Innate weather - Varies by season; Camo - Random
Nature Power - New Season; Secret Power - Paralyze foe
Spring=Rain, Summer=Sun, Fall=Sandstorm, Winter=Hail *Changes automatically every 5 turns

10.Lost Woods (Legend of Zelda: Link to the Past)
Innate weather - None; Camo - Grass
Nature Power - Razor Leaf; Secret Power - Poison foe

14.Final Destination (Super Smash Bros. Melee)
Innate weather - None; Camo - Fighting
Nature Power - Baton Pass; Secret Power - Foe's Defense down

15.Gangplank Galleon (Donkey Kong Country)
Innate weather - Sunny; Camo - Water
Nature Power - Headbutt; Secret Power - Confuse foe

16.The Flying Kroc! (Donkey Kong Country 2: Diddy's Kong Quest)
Innate weather - None; Camo - Steel
Nature Power - Bounce; Secret Power - Randomly Poison, Burn, or Freeze foe

Pokémon Battle Revolution
Here are the Colosseums from Wii's PBR. A lot of them share their terrain effects, but you can still use them for aesthetics. Or you can try out the special rulesets. Just be sure to have fun in Pokétopia! (Camo effects are untested, but probably correspond to the DPPt terrain, same as Nature and Secret Power)

Gateway Colosseum
Innate weather - None; Camo - (untested)
Nature Power - Hydro Pump; Secret Power - Foe's Attack down
Special Rule - Rental Battle

Main Street Colosseum
Innate weather - None; Camo - (untested)
Nature Power - Tri Attack; Secret Power - Paralyze foe
Special Rule - None, standard knockout battle

Waterfall Colosseum
Innate weather - None; Camo - (untested)
Nature Power - Seed Bomb; Secret Power - Foe goes to Sleep
Special Rule - Team Battle

Neon Colosseum
Innate weather - None; Camo - (untested)
Nature Power - Tri Attack; Secret Power - Paralyze foe
Special Rule - Fortune Battle

Crystal Colosseum
Innate weather - None; Camo - (untested)
Nature Power - Rock Slide; Secret Power - Foe will Flinch
Special Rule - Tournament Battle

Sunny Park Colosseum
Innate weather - None; Camo - (untested)
Nature Power - Seed Bomb; Secret Power - Foe goes to Sleep
Special Rule - Little Battle

Magma Colosseum
Innate weather - None; Camo - (untested)
Nature Power - Rock Slide; Secret Power - Foe will Flinch
Special Rule - Round Battle (?)

Sunset Colosseum
Innate weather - None; Camo - (untested)
Nature Power - Earthquake; Secret Power - Foe's Accuracy down
Special Rule - (Pick from a pool of 12 rental pokemon) Battle

Courtyard Colosseum
Innate weather - Deep Fog or None (random); Camo - (untested)
Nature Power - Tri Attack; Secret Power - Paralyze foe
Special Rule - Survival Battle

Stargazer Colosseum
Innate weather - None; Camo - (untested)
Nature Power - Rock Slide; Secret Power - Foe will Flinch
Special Rule - Master Battle