Via Nick Packwood (best known as Ghost of a Flea), I just learned about the discovery of the cave where a she-wolf crossed species lines and suckled Romulus and Remus — “twin sons of the priestess Rhea Silvia, fathered by the god of war, Mars.” But for this touching act of inter-species (trans-species? and how about trans-mortalist?) altruism, Rome never would have been founded.
How did the helpless twin demi-gods end up in a state of animalistic dependency?
Glad you asked! Their mother was the daughter of the Trojan-descended Numitor who shared the Alba Longa kingdom with his twin brother Amulius, who tried to stop Numitor’s daughter from having children:

Because Amulius held the treasury, thus having more power than his brother, he dethroned Numitor as the rightful king. Out of fear that Numitor’s daughter, Rhea Silvia, would produce children that would one day overthrow him as king, he forced Rhea to become a Vestal Virgin, a priestess sworn to abstinence. She was discovered to be pregnant nevertheless[4] She bore the twin boys, as told, of remarkable size and beauty, later named Romulus and Remus. Amulius was enraged and ordered Rhea and the twins killed. Accounts vary on how; in one account, he had Rhea buried alive (the standard punishment for Vestal Virgins who violated their vow of celibacy) the death of the twins by exposure; In another, he ordered Rhea thrown in the Tiber with the twins.
The servant ordered to kill the twins could not, however, because they were too cute and innocent, and placed the two in a basket and laid the basket on the banks of the Tiber river and went away. The river, which was in flood, rose and gently carried the basket and the twins downstream.

The kindly she-wolf took pity on them, and the rest is history.
The grotto is very fragile, they’re afraid it will collapse, but it has been photographed with probes:

November 20, 2007–Colorful mosaics spiral across the vaulted ceiling of a grotto that was unveiled today as the likely place where ancient Romans believed that a she-wolf suckled their city’s legendary founders.
In January archaeologists announced that the sacred cave, known as the Lupercale, had been found during excavations of Emperor Augustus’ palace on the Palatine, a 230-foot-tall (70-meter-tall) hill in the center of Rome.
According to Roman myth, a female wolf nursed the abandoned twins Romulus and Remus in the Lupercale. The grown brothers are said to have founded the Eternal City at the site on April 21, 753 B.C.
Since the grotto’s discovery, experts have been examining it with remote sensing devices, because they fear that a full dig might cause the already fragile cave to collapse, the Associated Press reported. So far the team estimates that the domed sanctuary is 26 feet (8 meters) high with a 24-foot (7-meter) diameter.

More here. It appears that the Emperor Augustus built his palace over the site for political reasons, but in any event its discovery is extremely important, for the Lupercalia was one of the longest-running and most important festivals in ancient times.
Amazingly, the Lupercalia was an annual celebration which lasted (although substantially degraded form) well into Christian times, until Pope Gelasius put an end to it in 494 A.D.
Interestingly, they failed to get rid of the name “February”:

The festival was held every year, on the 15th of February,a in the Lupercal, where Romulus and Remus were said to have been nurtured by the she-wolf; the place contained an altar and a grove sacred to the god Lupercus (Aurel. Vict. de Orig. Gent. Rom. 22; Ovid. Fast. II.267). Here the Luperci assembled on the day of the Lupercalia, and sacrificed to the god goats and young dogs, which animals are remarkable for their strong sexual instinct, and thus were appropriate sacrifices to the god of fertility (Plut. Rom. 21; Servius ad Aen. VIII.343).b Two youths of noble birth were then led to the Luperci, and one of the latter touched their foreheads with a sword dipped in the blood of the victims; other Luperci immediately after wiped off the bloody spots with wool dipped in milk. Hereupon the two youths were obliged to break out into a shout of laughter. This ceremony was probably a symbolical purification of the shepherds. After the sacrifice was over, the Luperci partook of a meal, at which they were plentifully supplied with wine (Val. Max. II.2.9). They then cut the skins of the goats which they had sacrificed, into pieces; with some of which they covered parts of their body in imitation of the god Lupercus, who was represented half naked and half covered with goat-skin. The other pieces of the skins they cut into thongs, and holding them in their hands they ran through the streets of the city, touching or striking with them all persons whom they met in their way, and especially women, who even used to come forward voluntarily for the purpose, since they believed that this ceremony rendered them fruitful, and procured them an easy delivery in childbearing. This act of running about with thongs of goat-skin was a symbolic purification of the land, and that of touching persons a purification of men, for the words by which this act is designated are februare and lustrare (Ovid. Fast. II.31; Fest. s.v. Februarius). The goat-skin itself was called februum, the festive day dies februata, the month in which it occurred Februarius, and the god himself Februus.

Alas! We’re still in the months named for numbers, and this November weather sucks, and makes me want to return to California.
February seems a long way off.
(And there’s no Lupercalia to look forward to!)
I guess the she-wolf was lucky that there weren’t any animal rights activists around to accuse her of “species-inappropriate” behavior.