Complex sentence: In 1447, King Alfonso V of Aragon built a Custom Palace to tax the local sheep farmers, but this caused a decline of the local economy and the progressive ruin of the land, which again became marshy.
Split into simpler sentences: In 1447, King Alfonso V of Aragon built a Custom Palace to tax the local sheep farmers. This caused a decline of the local economy and the progressive ruin of the land, which again became marshy.