Decide on a theme to choose the right location for a girl's birthday party. The theme can help you determine whether you should have an indoor or outdoor party and what your needs are from a location.
Since many children have things that are their favorite, whether it is princesses, superheroes or unicorns, it is fairly simple to come up with a theme. For theme parties, the location is usually not the thing the children remember the most. Outdoor locations, such as public parks, typically don't require a reservation. This can work in your favor if you are planning at the last minute. Parks offer the sort of space where it is easy to offer activities such as a scavenger hunt and provide great opportunities for photos.
If you chose to do an indoor location, the biggest thing to keep in mind is that you need to have enough space for everybody, and not just the children that are invited. Many of the children come with parents and even perhaps bring their own friends. Numbers can quickly exceed expectations. If having enough space is not an issue, the indoor party offers a level of reliability that an outdoor gathering can't provide: weather is not an issue, random people that were uninvited are not a concern, and you get more time to setup and clean up.