Arena_Discovery is set in a cliffside-excavation of an old Mayan waterfall temple.
Arena_Discovery was intitially concepted as a submission to a Tf2maps.net project called The Pacific Pack (which also spurred the development of an in-game and popular map Koth_Suijin). The Pacific Pack was never completed as a whole, but I felt quite inspired by the unique style of Bali and a the idea of a huge waterfall temple, so I continued with it.
The map takes design inspirations from the official map Arena_Nucleus, which features a cool mechanic that after 60 seconds (the standard point unlocking time in Arena mode in TF2) bridges open up and stretch across its center which allow easy access through the map. The average arena-mode round time is 1 minute 30 seconds; having the map effectively be easier to traverse as the round progresses means you can get closer to your opponenets quicker as the alive-players population drops.
The map design changed a lot even though it doesn't quite look it in the development images. The map's size was the biggest change. Arena mode automatically adjusts the team sizes down to a maximum of 8v8 by default (you can disable as a server op, though) because the intitial combat interaction of both teams tends to be a massive spam slog! And from testing I found that having smaller team sizes felt comfier / better on a smaller map but with greater changes in heights. So you felt still like you were close enough to other players, but were given an intricate-enough space with which to surprise other players (important since it is last-man-standing).
The detail of the map is heavily influenced from similar styles of cliffs from Bali. It is a really close-to-my-heart special feeling knowing that the calming meditative feelings of wanting to spend time in the map I've created is based on real locations in Bali. Someday I could go visit (if I can stand the 99% humidity) that true place and feel nostaligic even though I haven't been before. It's a crazy thought!
How big the first wave of spam is in arena mode. You notice it while playing, that there tends to be a huge first engagement, and that the best option for survival (on most maps, some are okay actually) is to forego the first battle, and wait for the spam to clear a bit.
Some maps like Offblast have many different routes available for players to go which lets them bypass where they might predict the spam to occur at, other maps like Well allow players to bypass the spam by using alternative routes towards the center of the map like the balconies or water routes, which have different pros and cons which also add to depthful predictions of if its worth taking or not, or predicting if the enemy is going to take those routes, etc.
The idea of opening up routes later into the map, in arena maps, is really cool. As the player count goes down, especially on the few last players, having more options to evade or attack the few remaining enemies adds to the feeling of being close to the other players - speeding up the intensity, and it also of course gives you more variance in how the battle might play out.
It is a really cool feeling when you know enough about the game that you predict on-the-fly how a battle might play out and aim at the perfect location just as a player walks out, and you follow it up with shots. Just makes you feel like you're really in-tune with the game. Flows really well.
The bonus powerup item was added in somewhat late in development, and it was simply added in because I wanted more variance and uniqueness in the map (people did look out for the powerup spawning in certain rounds!). Initially it was only a small buff of speed, but we found that it really just wasn't 'special' enough; it really didn't stand out that much in your mind after playing the level.
Changing it to be overpowered in gameplay, even at the cost of balancing, felt okay in the end because it added the challenges of not only to being able to fight against such a player weilding the powerup, but also to be the first player at the powerup spawning location - inciting proper fast rollouts. It did in fact lead to some interesting additional goofy depth!
Here's a video from an esports TF2 youtuber eXtelevision highlighting some competitive 5v5 gameplay on the map.