The Western Wall
The Western ("Wailing") Wall and tunnels. The wall is part of the retaining wall of the Temple Mount[a].
The "Wailing" being spoken of in the name of the wall is wailing over the hardships the Jews have endured ever since the Romans came and steamrolled their revolt in 70 CE. In particular, the loss of the temple (razed by Romans along with the rest of Jerusalem) and the ban on Jews entering Jerusalem - unless they paid for access, and then for one day each year (9th of Av[b]).
Jews may often be seen sitting for hours at the Wailing-place bent in sorrowful meditation over the history of their race, and repeating often times the words of the Seventy-ninth Psalm. On Fridays especially, Jews of both sexes, of all ages, and from all countries, assemble in large numbers to kiss the sacred stones and weep outside the precincts they may not enter.
— Charles Wilson, 1881. (Picturesque Palestine, vol. 1, p. 41[c]).