This REALLY needs a lot more context. Not even joking there is no way to give an appropriate answer here.
For one, what type of duel. Swords? Guns? Cards?
You have stated that this is a card dueling series, but are there other duels that you are looking for inspiration for, or just locations for the card duels outside of general arenas?
Secondly, what is the lore of the universe? What level of magic exists?
Generally card duel games are a theme of anime and a lot of occult aspects in a number of anime are linked to religion in some way, whether it be modern religion or ancient long forgotten by most people religion, though it isn't always the case.
In either case, I would have my duel in a sea parted by magic with the heavens opening up overhead and battle music played by angels pouring down from above. Over the top and overly dramatic? Yeah, but that's how I like it. Be it with swords or cards that's where I'd duel. Guns would be somewhere like a shopping mall with lots of cover where it turns more into a hunt than a duel, or is more like the Matrix lobby scene than you're classic gun duel.