Complex sentence: Buildings in the Gothic and Renaissance styles--palaces, churches and monasteries--were all in ruins, with only the Sponza Palace and the front part of the Rector's Palace at Luza Square surviving.
Split into simpler sentences: Buildings in the Gothic and Renaissance styles--palaces, churches and monasteries--were destroyed. Of the city's major public buildings, only the Sponza Palace and the front part of the Rector's Palace at Luza Square surviving.