The central regions of the Milky Way contain the most extreme stellar cluster known, the majority of the stellar mass of the Galaxy, most of the spiral structure, much of the star formation, all of the disk bar (if it exists), the mysterious central bulge and nucleus, the inner molecular ring, and many examples of rare and extreme states of stellar and dynamical evolution. From the ground most of these are confused in projection and obscured even in the near IR, and it is impossible to make a systematic large scale search in the IR beyond the L band (3.5mu). From space, only low sensitivity and/or low spatial resolution data exist thus far, so that our understanding of the inner Galaxy remains superficial. ISO, combined with the coming near IR surveys, DENIS (in which we are engaged) and 2MASS, will fundamentally improve our understanding of the inner Galaxy (structures, stellar populations, extinction...). The sensitivity and the angular resolution of ISOCAM are sufficient to detect sources of the dominant stellar populations (red giants) at the Galactic centre, the wavelength chosen (15mu, LW3) is far enough from those accessible from the ground to provide entirely new data and to escape reddening, while not being so red as to prevent easy 2mu identifications of individual sources. A large survey is critical, as in any single line of sight foreground and background are inextricably confused unless one can resolve individual sources, and obtain complementary data to identify (statistical) distances. A large area is also needed for statistics on rare populations, such as mass-losing AGB stars, and thus for scientific goals such as the total amount of matter fed by the stars to the interstellar medium. Similarly, many of the fundamental structures in the Galaxy are seen preferentially on scales of tens of degrees. We propose an ISO 15mu survey of 15 deg^2 in selected areas of the central l=+/-30deg of the Galactic Plane, additional colour mapping of the central cluster, all complemented by our 0.8-2.2mu DENIS data.