Yeah? Well, I'd like to see one, as well!
Have you actually read the books in question? If not, I'll say that all we ever see of the interior of this monster is (1) the multiple layers of kilometer-thick airlock doors leading to the innermost chamber and (2) said innermost chamber which was the size of, and had the look & feel of, a small park. The park contained 3 houses and a small control room building, as well.
We're told the 1 cubic km of Brain that runs the thing is "underground" in relation to the houses, but we never see it once the ship has been constructed. (The Brain was built first, then the ship was materialized around it.)
Other than that, all we're told in the books is that the main sixth-order drive engines, main power plants, shield generators, etc. are within a spherical area about 100 km in diameter that makes up the core of the vessel. We know this because at one point, the Valeron is hit with such an attack that she gets mostly vaporized -- peeled like an onion -- by such strong forces that the creator has to re-tune the shield generators to protect only the vital 'interior' instead of protecting the whole vessel. Only with the supposedly invincible screens doing a 200x overlap over a much smaller area does the core of the ship survive the attack and escape.
[by the way, if you're not familiar with "Doc" Smith's over-the-top style and love of synonyms for 'huge' or 'gigantic', the end of this particular series will illustrate it quite nicely. Determining that the antisocial race that runs the galaxy which nearly destroyed his vessel has GOT to go (it's a threat to all humanity everywhere, y'see) the creator of the Valeron with some help from notable allies and one major enemy, destroys said enemy galaxy. Yes, the galaxy. Actually, he destroys two galaxies, because he uses the stars from one galaxy as ammunition to destroy the stars in the enemy galaxy. (He picks a star in the enemy galaxy, determines its direction and velocity; picks a like-sized star from the 'ammunition' galaxy with a diametrically-opposed velocity, and flips the 'ammunition' star through the 4th Dimension so it reappears in the path of the enemy star. Splat, Kaboom: super-super-super nova. Wash, rinse, repeat. Since nearly every star in the enemy galaxy had a planet of the enemy around it, pretty much every star gets destroyed.]