Basic design looks like this:
www.harpsofpraisehf.com/images...ack.jpg
www.sunflowermusic.nl/harp.jpg

"Gothic" is a kind of catch-all term for the style of harp-body that was used on the Continent, in the Middle Ages and Renaissance.

At that time continental harps were mostly gut-strung, which meant the string had to be about 30% longer than the corresponding wire strings to produce the same note. So it's a taller & more lightweight design than the traditional shape of the Celtic harp (which had to be very squat and sturdy, to take the ungodly tension of wire strings without cracking the wood.)

Many modern Neo-Celtic harps incorporate design features from both models.