Why is the article grammatically correct in "the pyramids"? [closed]

Could you please explain to me why we add the definite article "the" to "pyramids" -----"The pyramids" even though it's a plural noun.

The grammar rule says, that we add article only to single nouns.

There's no rule that says definite articles should only apply to singular nouns. A definite article just means that the item(s) you refer to are in some way set apart from the general class of items by relevance, proximity, or previous reference. Consider:

Put the books on the shelf.

The dogs barked loudly.

I walked the streets alone.

When talking about the generic structure of a pyramid, I've never seen anyone use "the pyramids".

However, even though there are pyramid structures all over the world (e.g. Sudan, Nigeria, Greece, Spain, China, India etc...). arguably the most famous pyramid structures are The Egyptian Pyramids. So when someone says "The Pyramids" it's basically a short-hand way of saying "The Egyptian Pyramids".