Hi Tara, They are identical. Chinese is not that logical for some reason. 怎么走 has already expressed how to get to 天安门，which implies that you are going to 天安门。It's fine. However, sometimes, people might arbitarily say 去天安门怎么走 in which the word 去 is redundent, but it can be used this way.

去天安门怎么走 and 天安门怎么走? 去天安门 = go to, get to ...... Literally，怎么走 = how to walk, how to go; but this phrase have an idiomatic meaning: through which path can I get to （a place）. It's particulally used to ask for the way to somewhere. 去..... 怎么走？ 是 normal， and ...... 怎么走 is less grammatical and and more colloquial, but it frequently appears in everyday Chinese. You may deem it as an illipsis of 去。

去天安门怎么走 and 天安门怎么走? 去天安门 = go to, get to ...... Literally，怎么走 = how to walk, how to go; but this phrase have an idiomatic meaning: through which path can I get to （a place）. It's particulally used to ask for the way to somewhere. 去..... 怎么走？ 是 normal， and ...... 怎么走 is less grammatical and and more colloquial, but it frequently appears in everyday Chinese. You may deem it as an illipsis of 去。

They are both correct, no big difference.