A national heritage site is a very special place that people from a whole country have decided is very important to keep safe and protected. It's a place with a lot of history, meaning that it's been around for a very long time and lots of important things have happened there.
Think of it like a treasure or a magical diamond that belongs to everybody and everybody wants to keep it safe forever. Just like you might have a special toy that you really love and want to make sure nothing bad happens to it, a national heritage site is like a special toy that a whole country loves and wants to protect.
National heritage sites can be all kinds of things, like a big castle, a really old bridge, or even a really beautiful forest that has been around for a long time. People visit these special places to learn about the past and feel connected to their heritage, the stuff their ancestors did before them.
So just remember that a national heritage site is a super-important place that belongs to every person in a whole country, and we all want to make sure it stays safe and protected forever!