Using location words with Subject/topic markers

Question

I can't really figure this out myself so I don't think I can really give an example for this question so I'll just ask it and if it's too obscure to really answer say something in the comments and I'll try to add to it.

So, you guys have really been helping me out explaining は and even が a little in a previous question, but now I'm wondering about marking location words with は and が.

I know that usually に and へ usually mark the thing to which you do something and で usually marks where something takes place or by the means of which you do something (by/with). So how do I know when to use a subject/topic marker to mark words like きっさてん、 としょかん、 がっこう etc. that would usually take に, へ, and で. I'm pretty sure I'm overthinking this, but whenever I start a sentence like this がっこう に I'm always wondering if it shouldn't be the topic or subject or something. Forgive the probably somewhat vague question, but I seem to have a lot of problems/questions when it comes to particles.

Answer 1

I'm not sure I understand what exactly you're asking and I don't know if this helps, but objects can also be the topic of a sentence (には, では, へは), but objects can't be the subject of a sentence.

If you want to use がっこう as an object, you can say がっこうに. If you want to also make this object the topic of the sentence, you can use がっこうには.

If you want to use がっこう as the subject, you use がっこうが. If you want to also make this subject the topic of the sentence, you use がっこうは.

Whether がっこう becomes the topic of the sentence is independent of it being an object or a subject. But がっこう can only be either an object or a subject, never both.

がっこうには　とけいが　あります。
At the school there is a clock.

(スーパーは　でんしゃで　10ぷんのところに　あります。)
がっこうは　ちかくに　あります。
There is a school in the neighbourhood.