Stronghold

A stronghold is a structure that occurs underground naturally in the Overworld and is the only way to access an End portal. Strongholds can be located by using eyes of ender, or using the world seed in a tool like amidst. In Minecraft Java edition, there are 128 strongholds in each world. This should be the number of strongholds on the server, but for unknown reasons, many strongholds didn't spawn where they were supposed to spawn. This means that the stronghold count is likely below 128 but is still unconfirmed.

Current Events
The GGG public infrastructure group is currently in the process of scouting out all 128 strongholds on the map. WIP

Closest Stronghold to Spawn
The closest stronghold to spawn is widely used by the player base. It can be accessed using a Nether portal on a branch of the +X Nether highway. The portal is currently inside an obsidian room due to constant griefs destroying the rest of the stronghold and island above.

Other Strongholds
The strongholds are in eight rings around spawn, with the outermost having a radius of 25k. At least one stronghold on the outermost ring was used as a stash for the End portal dupe. These can easily be found by inserting the world seed into a stronghold finder. Most, however, are still widely untouched and unexplored. For unknown reasons, several strongholds did not generate on 9b6t.

Here is a table of all strongholds on 9b6t:

Artificial End Portal
There is also an end portal near the world border, which was built by Neobenedict to help CyberTF2 get back to spawn and Go_Hoosiers later built a stash around that portal, in order to be able to transport items quickly and to have an advantage during the Post-Dupe War. Go_Hoosiers revealed this secret on November 19t 2020, a day before the server shutdown.