Here is a big portal I use as an entrance for my underground city. Theme is obviously asian and I built it because I didn't find n appropriate model.

Inspiration came from the awesome Oriental Build Pack by Korea Artist, be sure to check it out, it's really worth it.

Frame size is 31, 23, 10 (X, Y, Z)
The space between the main pillars is 11 blocks

My advice is to change the banner show the beginning of your place.

You can use it in your creation, credits is always appreciated and diamond too :)

Keep crafting !