A windowless skyscraper in the heart of New York City may be the secret Manhattan surveillance hub of the US National Security Agency (NSA), The Intercept has reported. The brutalist, 29-storey AT&T Long Lines Building at 33 Thomas Street has sheer concrete walls that could reportedly survive an atomic explosion; inside, documents leaked by NSA whistleblower Edward Snowden suggest is one of the agency’s most important spying centres.