You see a marvellous sunken garden nicknamed the "hippodrome" because its shape resembles a stadium; its creator, the emperor Domitian, must have been fond of this shape because he built an actual stadium in the Campus Martius, Region IX center. Its fountains, trees, shrubs, and flowers are surrounded by a portico two stories high. This image shows the east end of the garden, while this model of the whole complex illustrates the overall shape of the hippodrome and gives some idea of the grandiose size and scale of Domitian's building plans.
Domus Augustana