Other Portal

An other portal is a manufactured structure that acts as a gateway between the Overworld and missing dimension.

Creation
A other portal is built as a vertical, rectangular frame of glowstone (4×5 minimum, 23×23 maximum). The four corners of the frame are not required, but portals created by the game always include them, resulting in 4 free/extra glowstone. Adjacent portals can share glowstone blocks. A other portal cannot be built horizontally like an end portal.

Once a frame is constructed, it is activated by water placed inside the frame. This creates portal blocks inside the frame, resembling a vortex. The water can be placed in any manner, including use of water bucket, dispensed by dispenser or natural spread of water. Other portals can be activated only in the Overworld or the Nether; they cannot be activated in the End and customized dimensions.

The water must be the last placed block in the structure—a water on an incomplete frame does not result in the portal activating upon the placement of the last glowstone block.

Behavior
When a player in the Overworld or the Nether stands in an other portal block for 4 seconds, the player is teleported 500 blocks in the air and  appears in the chat. The player can step out of a portal before it completes its animation to abort the teleport. However, in Creative, the wait time is one game tick ($1/20$ second) for the player to transfer between dimensions.

Most entities can travel through portals, including mobs (except the wither and ender dragon), thrown items, and transportation without passengers (neither mobs nor player), including boats, minecarts and horses. Unlike players, other entities travel through portals instantly, and once they reach the other side, there is a cool-down time for 300 game ticks (15 seconds), in which they cannot go through any other portals. Therefore, an entity can only travel though other portals again, once it is not touching any other portal for 15 seconds.

Issues
Other portal is an unsupported structure due to being an April Fools' joke, and therefore such issues relating to them will not be fixed.

Trivia

 * The other portal is likely a reference to the |The Aether mod, a dimension mod wherein players were able to build a portal out of glowstone and activated with water that would transport the players to a Heaven-like dimension, serving as a counterpart to the Nether's hellish environment accessed through an obsidian and fire portal. In its heyday, the mod was easily one of the most popular and iconic Minecraft mods, leading some players to be misled into believing it was actually in vanilla Minecraft, leading to disappointment upon finding out such a portal couldn't be built in the vanilla game. While the developer of the Aether mod, kingbdogz, has actually been hired by Mojang, there are currently no plans to add any new dimension to Minecraft, Heaven-like or otherwise, as adding a new dimension would divert attention away from fleshing out the existing ones.