Complex sentence: The construction of the Royal Palace was ordered by the Regent Maria Cristina, who wanted a new, worthy and sumptuous residence for the Court in 1645, when the Regent's son was about to come back from the Civil War.
Split into simpler sentences: The construction of the Royal Palace was ordered by the Regent Maria Cristina, who wanted a new, worthy and sumptuous residence for the Court. This was in 1645, when the Regent's son was about to come back from the Civil War.