The Court of Neptune Fountain - Washington, DC - Smithsonian Art Inventory Sculptures on Waymarking.com

In the center is Neptune, king of the sea. On each side of him are two separate castings of his two sons, each blowing into a conch shell. On the two side rocks are nymphs riding wild seahorses. There is great detail in all the castings and with water spouting everywhere, it does have a great feeling of the high seas.

The Court of Neptune Fountain can also be seen in Google Street View.

The fountain consists of a semicircular granite basin set in a retaining wall flanked by a set of stairs. Within the retaining wall, there are three large niches. Neptune, king of the sea, sits on a rock in the middle niche. Neptune is flanked by his sons, the tritons, mythological gods characterized by figures with the torsos of men and the fins of fishes. The tritons blow on conch shells like trumpets. In the niches on either side of Neptune, is a nymph riding a wild sea horse. Out in the basin four turtles, two frogs, and a sea serpent spray water. On the retaining wall, just above the niches, are reliefs of dolphins and stalactites.

From the Smithsonian AIC Remarks:

Albert Weinert was responsible for the reliefs of dolphins and stalactites carved on the retaining wall. The theme of the fountain relates to the Roman legend of Neptune, who became king of the sea after he and his brothers, Jupiter and Pluto, divided the world. Triton and Rhode were Neptune's children by his wife Amphitrite. Neptune won the heart of Amphitrite when he came riding to her on a dolphin.