The Estate contains large areas of private ancient woodland, the main area being Yardley Chase consisting of approximately 1,400 acres. The history of the Chase began when Judith, niece of William the Conqueror, applied to William II to enclose her own hunting area, which was granted.
There is an old brickyard on the Estate with its worked-out hollows and pits. The main pit is now a large pond. The Estate started making bricks and tiles on the site in the late 1800s to enable good quality housing to be built in Castle Ashby village. It has produced its own unique design of ridge tiles not found anywhere else. The pit ceased working in 1930 but one kiln is still standing. The little area surrounding it has produced some interesting botanical species and in the small spinney at the top of the hill is a memorial to the 6th Marquess.
The Castle Gardens are bordered by semi-wild ground and an arboretum with the main Park and Menagerie Ponds and the northerly Scotland and Grendon Quarter Ponds. This landscape was designed by Capability Brown in 1761. There are some terrapins in Grendon Quarter Pond which have survived there for several years. These surrounding grounds have retained some very interesting and rare plants as well as two ice houses and a lime kiln. Of course, there is a ha-ha to protect the formal gardens, all of these being good wildlife habitats.
The 14th-15th century Castle Church, dedicated to St. Mary Magdalene contains a good colony of Pipistrelle bats over the porch. White Butterbur - Petasites albus and winter Heliotrope - Pfragrans, together with a Foxglove Tree - Paulownia tomentosa planted in the mid 1930s by the 6th Marquess can all be found in the churchyard.