I have been dealing with this too. We have a couple of things that have teeny pieces (ala Playmobile) and a few things that the one year old would just plain wreck if she got her hands on them - puzzles, board games, etc.
We have explained to dd1 which toys dd2 can't be around because they are not safe around her or she is not safe around them. Dd1 has been really great about keeping things out of dd2's grasp when she knows they are not safe toys for her. But then, she likes to be in charge anyway.
So, what the kids do is play with things that are ok for both of them, and then sometimes dd1 has her own playtime with a puzzle or a game, say at the kitchen table or in her room, and we keep dd2 otherwise occupied. And dd1 will play with her "big girl" stuff when dd2 naps, too. All in all, I think they get plenty of playtime together, and dd1 likes having stuff that is all hers and baby sister can't play with.
As for physical locations, stuff that dd2 can't be into is either in bins in the family room that dd2 isn't strong enough to pull out or is in dd1's room.
HTH!