Switching cage

Question
My fiance and I just built our Holland Lop a 2 level Bunny Condo. We let her roam the house when we are home.
Her old cage was 28x26, how do you suggest making the transition from a smaller cage to a cage that is 4 times bigger. Do you think she will be scared of a bigger space or get used to it quickly.
Would I just open the door and let her do exploring?

Answer
You've hit on the answer yourself.  

Just open the door and let her check it out.  Rabbits are curious and she'll probably check it out on her own.  If she seems less secure in the bigger cage, you can provide a box for her to go into to help her feel secure.  Many rabbits like boxes to hang out in anyway.  You can also put some hay or a favorite treat in the cage to get her attention if she seems unsure about it.

One other thing, when some rabbits move to a new cage, it will appear that they've forgotten their litter box habits and poop outside the box.  Don't be surprised if this happens.  If she does that it should stop in time as she is just marking the cage as her own.

Good luck with your bun and her big new digs