Extremely large carbon tubes, some exceeding 5 mum in diameter, were produced with both laser and electric are techniques using graphite, a transition metal catalyst, and a reactive third-body gas. We have named these structures carbon megatubes. They are the first carbonaceous tubes large enough to observe using optical microscopy. We also report the synthesis of what we believe to be the first self-assembled branched nanotubes. In addition to their extreme diameters and unique morphologies, X-ray photoelectron spectroscopy has shown that these tubes also contain a significant amount of nitrogen atom incorporation into the graphite lattice. Subsequently, these nitrogen functionalities were shown to interact with rhenium pentacarbonyl bromide and serve as anchor points to tether molecules to the surface of the tubules.