The first point you put into Destruction magic lets you stream jets of flame from your hands for twice as long as before. Every hour, you're making a major decision about your character's abilities. When that happens, you get a perk point: something you can spend on a powerful improvement to a skill you particularly like. That alone would feel a little too hands-off, but you also level up. There's always been an element of this practice-based system in Elder Scrolls games, but in Skyrim it's unrestricted - you don't have to decide what you're going to focus on when you create your character, you can just let it develop organically. Your character gets better at whatever you do: firing a bow, sneaking up on people, casting healing spells, mixing potions, swinging an axe. It's the best Indiana Jones game ever made. You creep through them with your heart in your mouth, your only soundtrack the dull groan of the wind outside, to discover old legends, dead heroes, weird artefacts, dark gods, forgotten depths, underground waterfalls, lost ships, hideous insects and vicious traps.
These places are the meat of Skyrim, and they're what makes it feel exciting to explore. It was 40 hours before I blundered into a dungeon that looked like one I'd seen before, and even then what I was doing there was drastically different. These were sparse and quickly repetitive in Oblivion, but they're neither in Skyrim: it's teeming with fascinating places, all distinct. It's hard to walk for a minute in any direction without encountering an intriguing cave, a lonely shack, some strange stones, a wandering traveller, a haunted fort. The landscape is a challenge, and travel becomes a game. Wherever you decide to head, your journey is split between scrambling up treacherous rocks and skidding down heart-stopping slopes.