Invisible Signals is a monthly open-form radio series that traverses archival fragments, field recordings and sonic atmospheres to examine the material and affective dimensions of imperceptible infrastructures. This month’s episode takes place during a recent trip to Puglia, moving through coastal landscapes, unfinished architectures and the underground chambers of the Grotte di Castellana. The caves were formed over millions of years by water and mineral deposits, while structures along the coast were abandoned before they were ever completed. Both remain open to new forms of inhabitation. I recorded sounds through walking and curiosity, and along these paths were traces of temporary shelter, lives shaped by precarity and addiction, distant voices carried from the sea, and encounters that revealed the paradoxes held within the same landscape. Inside the caves, darkness reshaped perception. Bats occupied the spaces above while stalactites and stalagmites continued their slow formation. The descent underground, the enclosed atmosphere and the weight of the summer heat altered my sense of orientation. The body began to listen differently. This episode brings together those field recordings with archival and archaeological fragments, allowing sounds to move between geological time, abandoned architectures and the lives that continue to inhabit them. Presented by artist and researcher Florence To. Visit invisiblesignals.org.