If you’re a big fan of NES Zelda then you will love Zelda Outlands. It is a hacked ROM but boy is it fun, and challenging!
From the website of the creator:
“Link will face dangers and traps unlike anything Ganon had ever devised. His adventure will span 18 new dungeons hidden within a completely unfamiliar terrain. Zelda herself will make appearances to help the hero, providing items and sage advice crucial to the new journey. Link has become very skilled in his familiar world of Hyrule, but skill alone is his only advantage — the land of the Outlands is a beautiful yet deadly world bearing no resemblence to his own cherished kingdom.”
If you want to play this game you can buy the cartridge but most people just play on their favorite emulator.