Mine would be built on/into a hill - 2 storeys at the front and 3 at the rear. Entry floor (ground at front, middle at rear) would have a large kitchen in the middle, open plan to a 'family room'. There'd also be a separate lounge and dining room, food pantry, 'butler's pantry' (for storing occasional-use crockery and glassware, and cooking/baking accessories so they don't clutter the kitchen) and large utility room. Full-height sliding glass doors across the back open on to a terrace over the pool room. Top floor has bedrooms - 3 en-suite - and my own little sewing room/snug! Bottom floor (built into the hill) is gym/sauna/pool suite, with the same type of sliding glass doors as the family room, leading to a paved patio area.
It's all planned in my head - but if the lottery win was a HUGE one, the plans are much more ambitious and involve five houses, garage and entertainment block and a stone circle!!