I want to take a girl on a vacation but I don't know where to plan it for. Any ideas?

Paris.
:)

A subcluded cabin where you could snuggle by the warm fire, like a ski trip or something. Or the beach like others have mentioned.

ask her where her dream vacation would be,then if you can afford it I definitely say do it ,if my boyfriend wanted to take me on my dream vacation and could afford it,it would just make my dream vacation all the more special.

The beach (hotel), whatever you two agree on

It all depends on what she likes. find out how she feels about certain things, certain places, etc. then plan for the place where its like her 'paradise'

I would take her to Tuskany...it very romantic and the place is gorgeous!

Depends on what she likes...cold weather or hot weather. cheat or exotic....stylish/classy or just the jungle and rain forest?
does she like shopping or adventure

It depends about your budget. Here are some ideas though.
1) Hawaii (It's so romantic)
2) The Bahamas (it's a great place with so many things to do)
3) Florida (it's simple and easy to get to)
4) Las Vegas, Nevada (what happens in Vegas, stays in Vegas)
5) California (it's very nice there)

Ask her where she wants to go. As long as it's not across the world or country it's fine.

damn you crazy bro. take her to the beach?

Take her to your mom's house. Just playin' man. go on a road trip to different places. take turns driving, stay at different hotels, cheap, expensive, and camp out too, buy a cheep tent
at walmart and 2 sleeping bags. build her a fire and roast marshmellows. if y'all find a cool place along the way, just stay there. if you get bored go somewhere else.

Most girls like the beach. Plan somewhere tropical. It's romantic and fun! You can lay on the beach all day, and go out at night.