Complex sentence: The building was located near the centre of the fortress, it had its own bath buildings and a range of store rooms around the outside; the presence of a second bath building is unusual as legionary fortresses generally had just one set of internal baths.
Split into simpler sentences: The building was located near the centre of the fortress and had its own bath buildings and a range of store rooms around the outside. The presence of a second bath building is unusual because legionary fortresses generally had just one set of internal baths.