Complex sentence: The foremost landmark on the banks of the river is the walled district of Intramuros, located near the mouth of the river on its southern bank and was built by the Spanish colonial government in the 16th century.
Split into simpler sentences: The foremost landmark on the banks of the river is the walled district of Intramuros, located near the mouth of the river on its southern bank. It was built by the Spanish colonial government in the 16th century.