Mosaics from the fabled Gardens of Lucullus, one of the pioneering influences on gardening, have been brought to light after 2,000 years by archaeologists in Rome.

The vast terraced gardens, or Horti, covered what is now the built-up area above the Spanish Steps. The first known attempt in the West to “tame nature” through landscaping, the gardens were laid out around a patrician villa in the middle of the 1st century BC by Lucius Licinius Lucullus, one of Ancient Rome’s most celebrated generals, after he retired in disillusion from war and politics.

They became a benchmark for all Roman pleasure gardens, and were taken over and developed by Roman emperors. The 1st-century mosaics decorated the nymphaeum, an artificial grotto with water features. One depicts a corpulent cupid riding a dolphin and another a wolf’s head in green and gold.

They were found nine metres (30ft) below street level during renovation work on the Hertzian Library (Biblioteca Hertziana), the German art history institute near the Spanish Steps run by the Max Planck Society.

Excavations below the library have also brought to light a marble head of Venus, perhaps a relic of the statues that once adorned the nymphaeum. Maria Antonietta Tomei, of the Rome Superintendency for Archaeology, said when workers began demolishing the interior of the building to modernise it “the architecture of the Ancient Roman garden appeared before our eyes. It seems like a dream.”

Andrew Wallace-Hadrill, director of the British School at Rome and a leading classical scholar, said Lucullus had invented the concept of the pleasure garden when he quit public life in disgust after his rival Pompey “robbed him of the credit for Rome’s conquests in the East”.

The historian Plutarch observed that Lucullus “abandoned public affairs either because he saw that they were out of control and diseased or, some say, because he had had his fill of glory and felt entitled to fall back on a life of ease and luxury”. Ironically, Pompey was himself outmanoeuvred by Julius Caesar in the struggle for power that marked the end of the Roman Republic.

Lucullus is said to have been inspired by Persian and Mesopotamian gardens that he saw during his military campaigns in Asia Minor.

Plutarch recorded that Lucullus “was the first Roman to lead an an army over the Tigris, taking and burning the royal palaces of Asia in the sight of their kings”, and that he funded his gardens – and his famous library and art collection – from “the spoils of the barbarians”.

Lucullus also built luxury villas and gardens with pavilions, belvederes and baths at Tusculum, in the Alban Hills near modern Frascati, and above the Bay of Naples, where he had channels cut to let seawater circulate in his fishpond. He is said to have introduced cherries and apricots to the West.

Stefania Trevisan, who is leading the dig, said that excavations were continuing in the hope of finding more remains. After Lucullus’s death the gardens were bought and embellished by the wealthy consul Valerius Asiaticus. The gardens were appropriated later by Messalina, the promiscuous wife of the Emperor Claudius, who forced Valerius Asiaticus to commit suicide. She in turn was executed in the gardens after plotting against her husband. When Claudius was informed while he was dining that Messalina was dead, he was said to have “asked for another glass of wine”.