The Hogwarts castle model Warner Bros. built for the original film series was preserved , not thrown away. It became a featured exhibit at the Warner Bros. Studio Tour London, where visitors can see the miniature castle used in the films.

What happened to it

The model was originally created for the movies as a detailed miniature used for wide shots and visual effects work. After filming ended, Warner Bros. kept it and later displayed it as part of the studio tour experience in Watford, London.

Why it matters

The castle is one of the most recognizable physical pieces from the original production, so keeping it on display lets fans see how much practical craftsmanship went into the films. It also serves as a permanent centerpiece of the studio tour, which has welcomed millions of visitors since opening.

In plain terms

So the short answer is: it still exists and is on display rather than being destroyed after filming.

TL;DR: Warner Bros. kept the original Hogwarts miniature and turned it into a museum-style exhibit at the studio tour in London.