If you're wanting this mountainous look or want to visit this old castle, be prepared for some hiking. The Arbuckle Mountains and Turner Falls are located near Ardmore, Ok.
Downtown Oklahoma City
I don't have a ton of places in downtown, but I do have enough to make a session! I recommend combining downtown with Myriad Gardens for more diversity.
Hafer Park is located in Edmond, Ok.
The Myriad Gardens is located in Downtown OKC and includes plenty of greenery, pathways, a pond, and depending on the time of the year, some flowers.
There are a few different areas around Sulphur, Ok. that I like to visit. Most of the area includes waterfalls, rocks, trees and more waterfalls :)
Sutton Wilderness Park
Sutton Wilderness Park is located in Norman, Ok. This is a very diverse area and includes trees, trails and open land. You'll find everything from wooden tepees to ponds, and maybe even some wildlife!
The Wichita Mountains are located in Lawton, Ok. There are a few places to visit; The Parallel Forrest and Mount Scott are just a couple of them.
Will Rogers Park
Will Rogers Park is located in Oklahoma City, Ok. There are walkways, bridges, ponds, trees and plenty of flowers when in season.