At the end, when Frodo is getting on the boat to run away with the elves. You see they've got this boat, which is a close apromixation to a viking longboat, but smaller and more elegant:

Now in the initial shot you have maybe five elves and gandalf. That's a lot of people. Then they add Bilbo. So they all get on this boat right. Now the boat in the shot is the section of the boat (again, relatively speaking) is the section marked A.
Now in the following shot the hobbits are crying and Frodo KISSES SAM on the head which I wouldnt do to my bestest of best friends in the fucking UNIVERSE. Wtf gay. So anyway that goes on and you see Frodo and Gandalf get on the boat. BUT YOU DONT SEE ANYONE ELSE ON THE BOAT!
So again referencing the picture above, this assumes that 5 elves and a hobbit are standing in the section marked B. How is that possible? How is that natural or comfortable? So I thought well maybe its magic, maybe in reality the ship is a PORTAL, or a wormhole. But looking at the structure of the ship again the only way, in terms of physics would be to have a stable wormhole which is afaik highly improbable.
So you could maybe have a black hole by the following theory:
8. A blackhole spins extremely rapidly. Its spin axis is the entry point to what we call a Wormhole. Any attempt to get closer to the blackhole center than the diameter of its event horizon, unless one is at the spin axis, causes one to vanish permanently from the observable universe.
9. A first approximation of a spinning blackhole would be a sphere with a hole from one side to the other at the spin axis. A second and better view would be of a spinning tube. The length of the tube is proportional to the blackhole mass. As a simplification we could say that the length of the Alchibah Wormhole Spin Tube is 47 light years. The tubes internal diameter is proportional to the rotational rate and the velocity of the object entering the Spin Tube. The outer diameter of the sphere or tube wall is the Blackhole event horizon. The inner diameter may be considered as the Spin Tube or Wormhole event horizon.
However this falls apart when you realize the blackhole would STILL be exerting gravitational forces regardless of it harboring a theoretical wormhole event horizon. SO the only answer is this. Lord of the Rings Trilogy is a Lost Season of the popular television show Stargate SG-1.

The size of the gate could have easily been masked off screen, the only problem would be its power source and im not sure how the elves swung that but im sure they probably had the SGC on the other side rig something so they could walk through.