How do you keep your toddler away from the Christmas tree?

My little girl is 20 months old and is a terror for pretty things...I just KNOW that this year she's going to go nuts for the tree. LAst year she wasn't so mobile...but I am a bit worried that she's pull it down now! I hjave already accepted that my collection of gl and antique ornaments will have to be left out of the tree decorating this year....but I still dont want the tree wrecked! I dont want to put it in a play pen ....my main room is notbig either...what can I do?