Complex sentence: The Sierra de San Pedro stretches for over 60 km in a NW/SE direction parallel to the Serra de São Mamede in nearby Portugal and is relatively lower than the latter.
Split into simpler sentences: The Sierra de San Pedro is a range of low hills that stretches for over 60 km in a NW/SE direction. It is parallel to the Serra de São Mamede to the west in nearby Portugal and is relatively lower than the latter.