Complex sentence: The Market Church itself houses a beautiful library, the Marian Library ("Marienbibliothek"), which is considered to be one of the oldest and largest church libraries in Germany, founded in 1552 by Sebastian Boetius, senior pastor of the church.
Split into simpler sentences: The Market Church houses a beautiful library, the Marian Library ("Marienbibliothek"). It is considered to be one of the oldest and largest church libraries in Germany, founded in 1552 by Sebastian Boetius, senior pastor of the church.