Inside the Church of Santísimo Cristo, in the lower part of the Cathedral of Santa María de la Asunción, there are remains of the Roman settlement that founded the city of Santander, including baths and fortifications. Other remains located correspond to streets, sewage systems and foundations of religious buildings prior to the current Church of Christ.
In the 1980s, Joaquín González Echegaray began restoration and recovery work in this area and as a result of this work, the remains of the baths and evidence of at least five periods of occupation from the 1st century AD to the 13th century, when the current building was erected, were found.
The remains of these thermal facilities consist of a hypocaust with at least nine lanes and an ashlar praefurnium. It is evident that this heating system devised by the Romans was intended for a thermal installation because it incorporates a water-repellent opus signinum.
The oven chamber is also particularly important because it was here that the heads of the martyrs Emeterio and Celedonio were kept during the Middle Ages, and around which the successive churches were built.
The location of these remains is evidence not only of the Romanisation of Cantabria, but also of the historical importance of the Cerro de Somorrostro.