When we took possession of the house we live in 10 years ago one of the hardest things I had to part with in order to make the house comfortable for a family of 4 instead of 2 was the window seat in what had been my aunt and uncle's bedroom. It made an "L" shape with windows on both arms of the "L". The longer side of the seat faced the west, with a big view and sunsets. The window on the short side of the seat faced the long second story deck. There were 3-inch thick black and white open-check flat cushions to lie on, and when you lifted those up – I thought this was the greatest when I was a kid – the top of each side of the "L"-shaped seat lifted up revealing a large storage space for blankets and stuff.
I felt terrible when it had to go to make room for the absolutely necessary small addition we made to the house, but in the hope that I'll someday find a way to have one again in my life, I always have my eye open for nice solutions that allow you to feel like you're outside when the weather forces you in. I saw this one on Contemporist, and it's by London based Platform 5 Architects. – GF