Monuments are also often designed to convey historical or political information, and they can thus develop an active socio-political potency. They can be used to reinforce the primacy of contemporary political power, such as the column of Trajan or the numerous statues of Lenin in the Soviet Union. They can be used to educate the populace about important events or figures from the past, such as in the renaming of the old General Post Office Building in New York City to the James A. Farley Building, after James Farley, former Postmaster General of the United States. To fulfill its informative and educative functions a monument needs to be open to the public, which means that its spatial dimension, as well as its content can be experienced by the public, and be sustainable. The former may be achieved either by situating the monument in public space or by a public discussion about the monument and its meaning, the latter by the materiality of the monument or if its content immediately becomes part of the collective or cultural memory.