How to introduce something new/unusual to a story?

[BitterBlue]

As in, something that is not reality but is an every-day knowledge to the characters int he story - like, superheroes are real or that everyone has blue skin and eight limbs. What I'm trying to introduce to the story is that the city/kingdom/something is completely surrounded by a heavily protected wall - and a few other things, set in a completely fictional universe. What I'm wondering is how to introduce these things without it sounding too fakey-fakey. Like, it's absolutely normal in their wolrd but alien in ours. Help?
Thanks in advaaaance!

 

[Kindness]

its easy, just talk about it like it should be there -- it wont seem out of place

like: sherley walked up the steps to her house. she checked her watch and sighed, a cloud of white vapour rising from her lips. she was late. then again, it wasn't her fault -- it had taken her almost an hour to get through the city gates, with the guards still stiff with suspicion following the princess' murder.
she looked back. she couldn't see the gates from where she stood, but the top of the wall that surrounded the city was visible above the roofs of the houses on her street. as she fished for her key she absent mindedly wondered how long it must have taken to create, etc, etc

its not the best example but the idea is that people just accept it because its fiction. so long as youre consistent with your story people wont raise an eyebrow at *anything* you slip in

 

[Nelly]

A really good way to do that is to have the characters in your story casually converse about a news story that relates to the topic. For instance... they could have heard that the wall around your city or whatever is being repaired, or that someone graffitied it, or something. If your universe has newspapers, televisions, etc., you could describe the story and then your character's reaction to it shows that the presence of [whatever] is pretty normal. Or just have it come up in casual conversation.