Extreme Stunt: Dive Rockstar
Extreme Location: Dive Rock
Extreme Gear: Acrobatics stat of 70+, Strong Potion of Fortify Health, Potion of Fortify Agility
High up in the Jerral Mountains is a rocky outcropping called Dive Rock. The vast majority of adventurers won't even come across this little Easter Egg. Dive Rock is north-northeast of Cheydinhal, but with no roads leading to it, can be nearly impossible to find. The mountainsides leading to location are extremely steep and will take time and effort to climb, even on horseback.
A far better path to Dive Rock is through Aerin's Camp. Experts in Acrobatics (at least level 70) can be referred to Aerin for advanced training. You'll find the camp north of Cheydinhal, and east of Azura's Shrine. You won't find Aerin, but her assistant will provide the training.
Once you've buffed up your Acrobatics stat, make your way north. There you may find the body of Andre Labouche, a luckless climber and adventurer whose corpse contains a letter leading into the unofficial quest "The Horror of Dive Rock." It's a touching little story, but one we won't spoil here.
Look up from that location and you'll see the small, rocky cliff high in the mountains. If you can manage your way to the diving board-like precipice, your journal will indicate that you've noted several new locations on your map thanks to the spectacular and unique view of the Imperial Province.
If you've finished (or rather, survived) the mini-quest, jack up your health with a potion or two and take the plunge - after you've saved your game. While not the highest location in Cyrodiil (the surrounding peaks in the Jerral Mountains are a bit higher), this is the loftiest natural cliff in the province. BASE jumping in Cyrodiil doesn't get more extreme than this.