\noindent The creation of strangeness and charm in nucleus--nucleus collisions at threshold beam energies is discussed as a probe for compressed baryonic matter. Experimental data on strangeness production at SIS energies indicate that the properties of kaons and antikaons are modified in dense nuclear matter. An experiment is proposed at the future GSI facility to explore the QCD phase diagram in the region of highest baryon densities. An important observable will be charm production close to threshold.

PACS numbers: 25.75.Dw