Niflheimr
Niflheimr is the realm all mortals & angels have to go to before they can travel to either the human realm or Angelheim. Because of how difficult the name can be to remember, a lot of people simply refer to it as Axel's realm, mainly because said realm is occupied by exactly one person. Said person is the gatekeeper himself, Axel Krieger.
Geography
Niflheimr is located in Gaiatine's skies, more specifically where the stratosphere is. Said realm is not visible by the human eye since it exists in a different plane, so the only way of accessing it from Altale is by visiting the Virgo Statue in Panna and placing a yellow flower on the base. Once it is done, whoever wants to visit Angelheim lands in Niflheimr, a small while realm with dense fog running on the floor. The only things found in said realm is a huge gate, a house & a modest garden. The weather in the realm depends on how Axel feels. It's usually clear, though. Sometimes it rains when Axel feels homesick (missing his family) or sad about being alone.
The only ways to exit the realm are either by passing the gate after Axel opens it, or by getting teleported to one of the realms by Axel. But, no one wants the 2nd situation to happen, as he only does so when he's about to transform into a dragon.
Short history: The realm did not exist until Axel was assigned to control who's going where. A small realm was made by the council of gods to help him accomplish his job more easily. To this day, Axel still has no idea how to make the realm's atmosphere look more lively.
Axel's house
Being the only inhabitant of Niflheimr, everything in the realm mostly has what he wants. The most notable feature in the realm besides the immense gate potentially scaring anyone who dares trespassing without Axel's permission, is the blue & white house close to it. While it is not mansion-sized, it is still bigger than the average house and was entirely built by hand by Axel himself.
A garden can be seen before entering his house. Said garden usually contains different types of hot peppers due to how much he loves eating spicy food, as well as a few types of vegetables (notably tomatoes) & some flowers (usually red, they remind him of his family).
The house itself is big enough for a small family to live in, but because Axel lives alone, he used many of the extra rooms to showcase all the souvenirs he gathered during his numerous trips for those who want to stay with him before they go to their destination. Oddly enough, Axel does not have a bedroom, as he hates sleeping on beds. Instead, a hammock can be found in the garden, and that's where he normally sleeps. Considering how much time he spends on cooking & crafting, he has a huge kitchen & a huge crafting room, where he has all the space he needs for his hobbies. Axel also has a living room where he'd like to install some technology (notably a television & a computer), but for now, he doesn't know how these things work.