The Lupercale (cave) (Rome)

 temple, monument, ruins, cave / cave(s), Roman Empire, grotto

From Wikipedia:

The Lupercal ("lupa", Latin for she-wolf) is a cave at the foot of the Palatine Hill in Rome, between the Temple of Apollo Palatinus and the Basilica of Santa Anastasia. In the legend of Rome's foundation, Romulus and Remus were found there by the lactating female wolf who suckled them until they were found by Faustulus. The priests of Lupercus later celebrated certain ceremonies of the Lupercalia there; from the late years of the Republic till A.D. 494, when the practice was ended by Pope Gelasius I.

In January 2007 Italian archaeologist Irene Iacopi announced that she had probably found the legendary cave beneath the remains of Emperor Augustus's house, the Domus Livia, on the Palatine. Archaeologists came across the 15-meter-deep cavity while working to restore the decaying palace.

On 20 November 2007 the first set of photos were released showing the vault of the cave which is encrusted with colourful mosaics, pumice stones and seashells. The center of the ceiling features a depiction of a white eagle, the symbol of the Roman Empire during the reign of Augustus, the first Roman emperor. Archaeologists are still searching for the entrance of the grotto.

Its location below Augustus' residence is thought to be significant; Octavian, before he became Augustus, had considered taking the name Romulus to indicate that he intended to found Rome anew.