The Japanese garden now incorporated in the 30-acre Atlanta Botanical Garden predates ABG by many years. It is the oldest part of ABG. A small sign inside the entry path notes the Japanese garden is undergoing renovation.
The Japanese Garden Research Network notes that pruned pines in this garden are Virginia pines, Pinus virginian. Maple, azalea, bamboo, and iris are among many plants inside and adjacent to this small walled garden.
The July 2011 issue of Southern Living contained an article on the entire ABG and 2010 expansion that doubled its area to the present size. http://www.southernliving.com/travel/south-east/what-to-do-at-atlanta-botanical-garden-00417000074415/

Moon gate just outside the Japanese garden at Atlanta Botanical Garden with a pruned pine to the right of this photo. A small lantern tucked into the greenery at the beginning of this path is featured later in this post.

Perpendicular to and beyond the Moon Gate to its right is another entry. This view shows two of the three walls (at the right) enclosing the garden.