This is something I started a while ago but only recently Completed. A Nether tunnel sometimes also called a nether hub is a way to make traveling around the nether easier and safer. It does this by eliminating Mob Spawning by having flooring made of slabs or transparent blocks which mobs can't spawn on, and by being enclosed inside of ghast resistant materials (any block with a blast resistance 3.5 or higher). It also helps prevent getting lost in the nether by being an enclosed structure.

The entrance to the Nether: In my base my portal is underground along with various other rooms like my crafting area and brewing station. I put the portal in a small room behind a piston door to keep Zombie Pigmen from wandering about my base and also to act as a mini Foyer for those who come to visit, as seen in its second picture I have my banners set up next to the door.

Portal Room on the nether Side: This is the main room of my hub, it has some iron bar windows looking out at the nether expanse from inside, from which you can also see the silhouette of the Nether fortress in the distance. The portal has my banners on each side, marking it as the portal to my base or an area built by me. The design of this nether tunnel is actually based off a design from a YouTuber I used to watch in the past named Dataless822, though his design originally used nether brick and a custom texture pack (Datacraft64x) that made it look red, mine uses Red nether brick so it is compatible (looks good) with the majority of texture packs, including the default one and Faithful (which is what I'm using here).

The main tunnel: This is a section of the main tunnel. The part with the banners leads to my portal room shown previously and the long hallway to the right leads to the Nether fortress. The entirety of the hallway is slabbed on the floor and ceiling to prevent mobs from spawning and give the room the feeling of having a regular un-slabbed floor.

The Exterior: This is the outside of the nether Tunnel in the spawn area of the nether, on the right you can see the large metal cage which extends out from the main spawn hub. I also slabbed this area around the entrance, the reason there is a section of nether brick slab as opposed the red nether brick slabs is because that was a pathway up top to access the fortress, though it's now redundant on the count of having the tunnel going there. I should note that I'm not the one who originally started slabbing the nether, that was done by someone else long before I joined the server, my work is just a continuation of it.