Gwydir is sited on the edge of the flood plain of the River Conwy, at the foot of a rocky crag, just over the river from Llanrwst (26555). It is notable for the partial survival of its sixteenth-century garden (86386). The estate is notable for having been owned and occupied by several generations of the Wynn family, and in the seventeenth century the gardens were known to have been of some sophistication.

Parc Mawr, the deer park associated with the house, lies south of the castle on the opposite side of the B5106. It retains much of its surrounding drystone wall and probably dates to about 1597. At its north end, opposite the castle, is the second area of the pleasure grounds, around Gwydir Uchaf, the main residence in the later seventeenth century. It was laid out with a summer house, a viewing mount, a viewing platform and (at a distance) a bowling green. There are also the remains of a contemporary family chapel (nprn 43667; SAM CN113). This area was linked to the castle by a zigzag path up the hill known as Lady Mary's Walk.