Section 416. United Nations

Real property owned by the United Nations or
  of any world-wide international organization of which the United  States
  shall  be  a  member  and  which  shall be established and shall provide
  international agencies in order  to  maintain  international  peace  and
  security,   develop   friendly   relations  among  nations  and  achieve
  international  cooperation  in  solving  international  problems  of  an
  economic,  social,  cultural or humanitarian character, by taking action
  which includes effective collective  measures  for  the  prevention  and
  removal  of  threats to peace, for the suppression of acts of aggression
  or other breaches of the peace and for the bringing  about  by  peaceful
  means,   and   in   conformity   with  the  principles  of  justice  and
  international law, of the  adjustment  or  settlement  of  international
  disputes  or  situations  which  might  lead  to  a breach of the peace,
  exclusively used for the purpose of establishing and maintaining thereon
  headquarters for offices and for places of assembly for carrying on  the
  functions  of  United  Nations  or  other  such world-wide international
  organization shall be exempt from taxation, special  ad  valorem  levies
  and  special  assessments.  The  exemption granted by this section shall
  continue with respect to such real property as long as  it  remains  the
  property   of   the  United  Nations  or  any  world-wide  international
  organization as herein described and is used exclusively for the purpose
  of maintaining thereon headquarters for offices and places  of  assembly
  for  carrying  on the functions of the United Nations or such world-wide
  international organization, and no longer. Any  building,  each  portion
  thereof,  and  the  land  on  which such building is constructed, to the
  extent and from time to time constituting  part  or  all  of  the  reuse
  project  defined  in  chapter  three  hundred  forty-five of the laws of
  nineteen  hundred  sixty-eight,  shall  be  exempt  from  real  property
  taxation,  provided  that  in  connection  with  such  reuse project, an
  agreement shall be entered into with the city of New York providing  for
  payments  in  lieu  of  property taxes with respect to any space in such
  reuse project that is not used for carrying  on  the  functions  of  the
  United   Nations   and  is  not  used  for  purposes  that  satisfy  the
  requirements for exemption  from  taxation  under  either  section  four
  hundred eighteen or section four hundred twenty-a of this article.