Minas Tirith is the capital city of Gondor from the Lord of the Rings movies. The city is absolutely massive, the creators of this have done a really good job of making this city as close as possible to the likeness we have seen in the movie.
The level is actually available for download, so if you like this you can have it without having to build it yourself. Click here to download the world.
According to the maps description by the maps creator the structure is 500 blocks wide and 300 blocks high, which is by no means the largest Minecraft creation we have ever seen, but the detail and accuracy when compared to the original is what makes this most impressive.