Battle Arena: Towers and Wasteland
I needed a simple map that could serve as a combat arena and that wouldn't take too much time to build. It also needed to be desolate and somewhere other than the material plan, so here we are. In my game the party is whisked away to this setting to fight each other to the death against their will by an extraplanar being that wishes to observe and analyze them during combat. They don't permanently die, and are whisked back to the material plane after the battle is won. To incentivize, the party is told that death in the arena isn't permanent and that the winner is awarded a permanent +1 to a skill. To ensure that the martials aren't outclassed by the casters, each party member gets to choose an ally that they control in addition to their own character. The martials get to choose between a slightly nerfed transmuter wizard or a master thief, and the casters get to choose between a slightly modified gladiator or a master thief.
The liquid on the map is acid, of course (!), and anyone who ventures into the courtyard to open a chest risks setting off the lightning tower found in the center of the map. Roll a D4 each time someone enters or starts their turn in the courtyard. On a 1 (or on a 1 or 2 if you want to add more risk) the tower targets everyone in the courtyard with lightning or a spell of your choice. The chests in the courtyard contain potions or wands.
There are several orbs in each tower. The larger orbs in the center transport the players up or down a level when touched, and the blue orbs on the second level of each tower will teleport them to the other towers that are nearest to them. You can add to the chaos by rolling a D4 when a blue orb is used. On a 1, assign each tower a number (1-4) and roll another D4 to determine which tower they will actually end up in. Using the orbs for transport may take a bonus action or full action if you want their use to have a cost.
This map could be adapted to any game that uses space travel or planar travel. Maybe it's an ancient ruin designed to house an artifact which is protected by powerful guardians who've hidden the item in one of the chests or towers. Use it how you like.