Neoclassical architecture is like building a big fancy castle out of blocks, but instead of just making it look cool, you use special rules and ideas to make it look extra special and fancy.
One of the rules is to make the building look symmetrical, which means everything looks the same on both sides. This makes it look really balanced and nice.
Another rule is to use columns, which are big sticks that hold up the building. The columns have special designs on them that make them look really fancy and important.
The last rule is to use decorations like statues, carvings, and paintings that show important stories and people from history. This makes the building look really important and fancy.
So when you see a big building that looks really fancy, like a museum or a fancy house, it might be built in the neoclassical style!