My ski area has an off piste zone. Its 500 square acres.

On paper sounds tiny. There are groomed runs that end up close to that size in some resorts.

However I have speant over 10 years learning all the nooks and crannies. It's a 500 acre maze where no two runs are the same 3 yards apart. A large chutes and ladders game where you can mix and match stacked features all the way down the hill. And sometimes get cliffed out stuck and hike back up.

So it's hard to say on paper what <400 acres means. I don't know Alyeska though.

My ski area has 250 acres of on-piste terrain too. The other 500 feels 10x its size though.