  We consider structured environments modeled by bosonic quantum networks and
investigate the probing of their spectral density, structure, and topology. We
demonstrate how to engineer a desired spectral density by changing the network
structure. Our results show that the spectral density can be very accurately
detected via a locally immersed quantum probe for virtually any network
configuration. Moreover, we show how the entire network structure can be
reconstructed by using a single quantum probe. We illustrate our findings
presenting examples of spectral densities and topology probing for networks of
genuine complexity.
