I wanted to build an OGame Death Star model in Minecraft, and I started doing it on the highest mountain I could find, for some reason... I built one third of it and blam, can't build any further! Why is that? Or is that a bug?
The Minecraft world is 256 blocks (as of Minecraft 1.2) from top to bottom. The reason for the height restriction is that the Minecraft world is made of 16x16x256 'chunks'. These are loaded into memory and rendered starting with the ones closest to the player. A 3D world of chunks (where the world is 'infinite' vertically as well as horizontally) is a whole lot more complex than a 2D world of chunks to manage, and optimizing for smooth gameplay would be a challenge. 256 is a convenient number that's a power of 2 (making it align nicely in memory).
Note that there is also a separate build height on servers. In the
server.properties file, there is a property
max-build-height which defaults to 256. Server admins can lower this value to prevent players placing blocks above a certain height, but it will not prevent natural terrain from spawning above this level, or players climbing natural structures above this height.
Although it is theoretically possible for a mod to increase the height limit of the map, I can't find any that work with the current version of Minecraft or are in active development.
If you want to build very high, build in the nether... That way you have plenty of space to go... Infinity. But in the over world, in order to build to infinity you need mods. The reason why there is a height limit is because the terrain would generate way to high, and the computer would lag or buffer and crash. The x and y dimensions also have a limit. 30,000,000 both sides. However, again, I have a question? Can't mojang set two height limits? One for the terrain, which is 256, or 512 and the building which is infinity?