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\section{Introduction}  Determining the structure of the Milky Way, from our vantage point within, within it,  is a perpetual challenge for astronomers. We know the Galaxy has spiral arms, but it remains unclear exactly how many, cf. \citep{Vallee2008a}. Recent observations of maser proper motions give unprecedented accuracy in determining the three-dimensional position of the Galaxy's center and rotation speed \citep{Reid2009,Brunthaler2011}. But, to date, we still do not have a definitive picture of the Milky Way's three dimensional structure. The analysis offered in this paper suggests that some Infrared Dark Clouds\footnote {The term ``Infrared Dark Cloud" or ``IRDC" typically refers to any cloud which is opaque in the mid-infrared.}--in particular very long, very dark, clouds--appear to delineate the major features of our Galaxy as would be seen from outside of it. In particular, we study a $>3^{\circ}$-long cloud associated with the IRDC called ``Nessie" \citep{Jackson2010}, and we show that it appears to lie parallel to, and no more than just few pc from, the true Galactic Plane.  Our analysis uses diverse data sets, but it hinges on combining those data sets with a modern understanding of the meaning of Galactic coordinates. When, in 1959, the IAU established the current system of Galactic $(l,b)$ coordinates \citep{Blaauw1959}, the positions of the Sun with respect to the ``true" Galactic disk, and of the Galactic Center, were not as well determined as they are now. As a result, the Galactic Plane is typically \textbf{not} at $b=0$, as  projected onto the sky. The exact offset from $b=0$ depends on distance, as we explain in \S \ref{lookingdown}. Taking these offsets into account, one can profitably re-examine data relevant to the Milky Way's 3D structure. The Sun's vantage point slightly ``above" the plane of the Milky Way offers useful perspective. [xxthis paragraph needs editingxx] IRDCs ``IRDCs"  are loosely defined as clouds with column densities high enough to be obvious as patches of significant extinction against the diffuse galactic background mid--infrared wavelengths.This implies that IRDCs are relatively starless: if they were to contain bright IR sources and nebulosity, they would not stand out as dark clouds. To give examples,  \citet{Peretto2009a} draw set  the boundaries of IRDCs at an optical depth of 0.35 at $8~\rm{}\mu{}m$ wavelength, equivalent to an $\rm{}H_2$ column density $\approx{}10^{22}~\rm{}cm^{-2}$. In their sample, clouds have average column densities of a few $10^{22}~\rm{}cm^{-2}$ (e.g., Figure~2 of \citealt{peretto2010:irdcs-mass-density}). Some IRDCsdo  actively form high--mass stars (e.g., \citealt{pillai2006:g11} and \citealt{rathborne2007:irdc-msf}). It is therefore thought \citet{kauffmann2010:irdcs} explain  that while  some ``starless"  IRDCs are {\it could be}  future sites of high--mass star formation. \citet{kauffmann2010:irdcs} demonstrate that most IRDCs are not massive formation,  anddense enough to form high--mass stars \citep{kauffmann2010:irdcs}. Still, they also argue that  the few $10^2$ hundred densest,  most massive and dense clouds massive, IRDCs  may very well  contain a large fraction of the star--forming gas in the Milky Way. In Way, it is still true  that case, most IRDCs are not massive and dense enough to form high--mass stars. Thus,  a small number of very dense and massive IRDCs may be responsible for a large fraction of the galactic star formation rate. The massive stars forming in these dense IRDCs are so bright, that rate, and an  extragalactic observers observer  of the Milky Way might see ``see"  IRDCs hosting young massive stars as the predominant mode of star formation here. Thus, if If  one can deduce the pattern of IRDCs that an observer outside the Milky Way would see, one can determine the Milky Way's (non-dark-matter) structure, from inside.(CB Note: these last 2 sentences are interesting -- does it contradict Jens' claims made about star forming efficiencies in IRDCs? Jens: changed text to highlight that high--mass SF is limited to the most massive and dense IRDCs. Then the argument still holds that bright stars may trace IRDCs. If this is to hold for Nessie, this cloud should exceed the mass--size limit from \citet{kauffmann2010:irdcs}.)  The traditional ISM-based probes of the Milky Way's structure have been HI and CO. Emission in these tracers gives line intensity as a function of velocity, so the position-position-velocity data resulting from HI and CO observations can give three dimensional views of the Galaxy, if a rotation curve is used to translate line-of-sight velocity into a distance. Unfortunately, though, the Galaxy is filled with HI and CO, so it is very hard to disentangle features when they overlap in velocity along the line of sight. Nonetheless, much of the basic understanding of the Milky Way's spiral structure we have now comes from HI and CO observations of the Galaxy, much of it from the compilation of CO data presented by \citet{Dame2001}.