because it is a specific name of something The Eiffel Tower The Golden Gate Bridge etc

(Why DO we add ...) A good question. After all, we say, of other famous palaces, "Buckingham Palace", "Sanssouci" and "Versailles", with no article. But then we also talk about "The White House", "The Louvre" or "The Nymphenburg Palace". I think it may be local usage, extended into more general language. And if I look up "Taj Mahal" in Wikipedia, I'm told it means something like "Crown of Palaces", in which translation it would be very natural to use "the" with it in English.

we can use these words to make a word specific : all possessives : my ,your ,his, her, their, and proper names "Where is Mohammad's house " Where is the/your/my/his/her house? this/that/these/those/which also make a noun specific. With names of proper places the use of "the" is not consistant, because sometimes people , especially the British, consider certain places to be an instituion , and therefore a collective noun and not actually a physical building, or just a place , like you say "I'm going to London" not "the London" Where is Parliment? Where is Buckingham Palace? Where is the Taj Mahal? Where is the White House? If I show you one case in America congress, which could be considered both a collective noun meaning the group of people that make our laws ,and also the group of physical buildings where they work, you can see the difference. "The president visited Congress today." "Will this bill pass in the Congress?" Where is the Senate? Where is the Statue of Liberty? and sometimes , like with streets, a proper name will also make a building specific: "Where is Camdon House?" With streets there never is a "the" because the name of the street specifies: Where is Oxford Street? Which street are you on? ---I am on Kinsington Street right now? Which Kinsington street? --The Kinsington Street in London. Here "the" is uses to differentiate from othe Kinsington Streets that exist in Britain.