Global maps of Titan show great diversity in terrain types, but their associations with specific compositions on a large scale are obscured by Titan's thick atmosphere, which shrouds the weak spectral features. Here we develop a principal component analysis (PCA) that enables the identification of subtle spectral features. The PCA was applied to over 13,000 Cassini/VIMS spectra that cover half of Titan's globe, focused on tropical latitudes. Our analysis detected an ice-rich linear feature of bedrock, which extends a length equivalent to 40 per cent of Titan's circumference. This corridor is puzzling because it does not correlate with topography or measurements of the subsurface. Ice-rich terrains in other areas of Titan occur only in local regions excavated by craters or exposed by erosion, suggesting that cryovolcanism, if active, is currently not widespread. We also find evidence for a diversity of organic sediments, formed by the photolysis of Titan's past atmospheres, which remain to be investigated, perhaps using a similar approach.