Niagara Falls, both the U. side and the Canadian side. Winter everything is covered with ice and snow -- and you can always find new things to see and do! It's an amazing (and VERY romantic) place to visit!
The Blue Mountains are located only by train from Sydney, Australia. It's the only place I've been that it's both a National Park and an amusement park: there is a skyway, a cable car and a railway(Favorite Places I've Been)
Muir Woods - majestic redwoods and the drive there is worth it. Listening to the San Francisco Symphony orchestra playing Dvorak, with the windows down, and the fresh air blowing in. Best way to unwind.
Although this is not a castle it is one of it best places I've ever visited in Germany. I had no other place to put it. Rothenburg ob der Tauber, Germany - 101 Most Beautiful Places You Must Visit Before You Die! – part 2