This garden, with its lagoon connecting it to Lake Carasaljo, is the most lavish of the three gardens designed by Bruce Price. It features a 17th century marble fountain from a garden in southern France (turned on only for special occasions) on a brick esplanade, a double marble staircase flanked by lions, and carved marble benches, which are copies of the benches in the Vatican Garden. The lagoon itself connects to Lake Carasaljo under a bridge also designed by Bruce Price. The bridge was restored in 1999. Water from the lagoon feeds the Apollo Fountain in the Italian Garden. Moss (Sawara) Cypress (Chamaecyparis pisifera) is common in this garden, but Eastern Redbud (Cercis canadensis), flanks the bridge at the southern end of the garden. The lagoon contains water lilies.

The sunken garden is most colorful between about April 10 and May 20, when the eastern redbud is in flower, along with the azaleas at the base of the double marble staircases and the crabapples on either side of the sunken garden. The crapemyrtles behind the 17th century fountain generally flower between July 15 and August 15.  October daisies are in bloom in October.