A perfect carbon nanotube with two closed ends consisting of graphitized carbon was experimentally observed. The large carbon nanotube, with a diameter of 187 nm and a length of 1.2 microns, was synthesized by pyrolysis of iron(II) phthalocyanine (FePc) under an Ar/NH3 flow at 900 degrees C on a nickel substrate. The structure and composition of the nanotube were determined by high-resolution transmission electron microscopy and electron energy loss spectroscopy. The carbon nanotube seems to grow spontaneously by some autocatalytic process.