The Far Lands are not exclusive to Infdev in fact, they first made their appearance in Infdev. The structure was used because there was no possible way to craft bricks. It is a completely solid structure, with no interior rooms. 14 minutes after brick pyramids were added, a quick update was released that fixed a bug where the structures would assume the world height was still 256 blocks, generate as such, and then get cut off by the lowered world height of 128 blocks. The base of the pyramid does not replace normally generated terrain except for water and air. These pyramids reached from near the top of the world down to the ground. The locations of the pyramids is predetermined, and was always the same regardless of the world seed, surrounding terrain, or game version.
The first version of Infdev, with a noticeable brick pyramid in the distance.
For a complete list of changes, see Java Edition version history § Infdev.
