||We propose to use the SPIRE-FTS to map a 8.5.x8.5. (~20pc x20pc) region around Sgr B2, the only source that allows studying a burst of star formation in the center of a galaxy (GC) with high spatial resolution even using a single dish telescope (25.. = 1 pc). Bright high-mass star forming regions do exist in the disk of the galaxy, but the specific location of Sgr B2 in the GC (where the ambient physical conditions are markedly different compared to the disk) make it the best source to compare with unresolved extragalactic nuclei (M82, the prototype starburst galaxy is ~400 times more distant and thus 25..=400 pc). Our SPIRE-FTS pointed observations around Sgr B2(M) core and surroundings show strong dust continuum emission as well as emission lines from 12CO and 13CO rotational ladders; [NII] and [CI] fine structure lines; emission-absorption of excited H2O and NH3, and line-of-sight absorption of a variety of light hydrides (HF, CH+, CH2, OH+, H2O+, H3O+, NH and NH2) that are difficult, if not impossible, to detect from the ground. Even far from Sgr B2 star forming cores, the expected continuum and line intensities will enable us to map tens of lines over large areas in very reasonable times. Understanding the large scale physics and chemistry of this starburst template in the GC is of great interest as recent Herschel observations are revealing similarly rich spectra in fainter galaxies where, of course, different components overlap in the beam. The proposed spectral maps and SEDs will form a large database that will be a legacy for higher angular resolution studies of extragalactic nuclei.