One possibility is that Harry Potter goes to church because he's on the run from some dark magic in the wizarding world. He thinks that the church, being a place of sanctuary in Muggle society, could offer him some protection. Once there, he might start to learn about Muggle religious beliefs and find some similarities between them and the values in the wizarding world, like love, kindness, and forgiveness.
Well, he might be quite confused at first. Churches are not really a part of the wizarding world he's used to. Maybe he'd be looking around in wonder at all the religious symbols and the way people pray.
In this fanfiction, Harry Potter could go to church to seek peace. After all the chaos and battles in his wizarding life, the quiet and solemn atmosphere of the church might attract him. He might sit there, thinking about his past, his lost friends, and find some solace in the religious environment. Also, he could interact with the local parishioners, who might be both curious and friendly towards this strange - looking young man with a lightning - shaped scar.
In such a fanfiction, Harry might go to Voldemort to try and reason with him. Maybe he believes there's a chance to end the war without more bloodshed. He could offer Voldemort a way out, like exile instead of death.
In this fanfiction, Harry might go to Diagon Alley to buy new school supplies. He could visit Ollivander's to get a new wand or Flourish and Blotts for some interesting magic books.
Well, he might encounter new magical creatures unique to PT. Maybe he'll learn some different spells or forms of magic there.
He might use magic to enhance his workouts. For example, he could use a spell to make the weights lighter when he's starting out and gradually make them heavier as he gets stronger. It would be really cool to see him combine his wizarding skills with gym exercises.
In fanfiction, if Harry Potter goes to Spain, he may discover new magical artifacts. Spain has a rich history, and there could be artifacts related to the Moors or other historical periods that hold great magical power. He might also have to adapt to the Spanish wizarding culture, which could include different festivals, traditions, and social norms within the wizarding community.
Perhaps he would find that the wizarding world has finally united with the Muggle world in harmony. Technology in the Muggle world could have influenced magic in strange and wonderful ways. He could be shocked to see flying cars that are now common, or houses that are built with a combination of magic and advanced Muggle construction techniques.
Well, if Harry Potter goes to France in fanfiction, perhaps he would visit the Beauxbatons Academy. He could learn about their different styles of magic education. There, he might make new friends and enemies. Maybe he'd get involved in some sort of international magical competition that involves both Hogwarts and Beauxbatons. And who knows, he could even discover some long - lost French magic spells that could help him in his future battles against the Dark Arts.
In a fanfiction scenario where Harry Potter goes to Pandora, he'd probably face a culture shock. The Na'vi's connection to nature is so different from what he's used to in the wizarding world. He could end up using his skills in potions to try and understand the biology of Pandora. He might also be in awe of the banshees and try to fly one using magic, which could lead to all sorts of adventures.
Well, perhaps Harry could discover a whole new magical world in Alfe. He might meet new magical creatures and learn different kinds of magic that are unique to that place.
He might use his magic to defeat the dragons in Skyrim. His spells could be a new and powerful force in that world.