Cefn Onn Park
This gem of a park is located on the northern outskirts of Cardiff. It has a large collection of specimen trees, rare plants and flowers with well surfaced, waymarked walking paths to follow. You'll also find rhododendron and azelea bushes, carpets of bluebells and buttercups, ponds and a gently trickling stream. If you'd like to continue your walk you could pick up the Rhymney Valley Ridgeway Walk which runs just to the north of the park and takes you through the countryside surrounding Caerphilly.
Parking is available at the southern end of the park. Lisvane & Thornhill train station is just a few minutes walk from the park so you can easily come by train too.