Complex sentence: The Church of Our Lady and St. Clemens Cathedral were built in the late 11th to 12th centuries and both have Romanesque features although they today have an ostensibly Gothic appearance from later alterations.
Split into simpler sentences: The Church of Our Lady and St. Clemens Cathedral were built in the late 11th to 12th centuries. Both have Romanesque features although the churches today have an ostensibly Gothic appearance as a result of later alterations.