In the 1870s, an excavation near the Temple Mount turned up a stone with a Greek inscription, reading, “No foreigner may enter within the balustrade around the sanctuary and the enclosure. Whoever is caught, on himself shall he put blame for the death that will ensue.” Another, similar stone was discovered in Jerusalem in 1935. These are thought to have been part of the Second Temple, most likely added during Herod’s major renovations during the 1st century BCE. Ilan Ben Zion writes:
Two millennia ago, the [stone] block served as one of several “Do Not Enter” signs in the Second Temple in Jerusalem, delineating a section of the 37-acre complex that was off-limits for the ritually impure [and non-Jews]. . . . [However,] the warning inscriptions point to universal inclusion—not exclusion—of Gentiles on the Temple Mount. . . .
Gentiles were not only welcome to ascend the Temple Mount, [as long as they did not go past the boundaries marked by these stones], they were also permitted, if not encouraged, to donate animals for sacrifice. [The ancient historian] Josephus recounts how Marcus Agrippa, Emperor Augustus’s right hand man, visited Jerusalem shortly after the Temple was built and offered up a hecatomb—100 bulls—as a sacrifice on the altar.
Read more on Times of Israel: http://www.timesofisrael.com/ancient-temple-mount-warning-stone-is-closest-thing-we-have-to-the-temple/