The first extension to the building was completed in 1537 and was commissioned by King Charles I . However , its exterior was constructed by the architect Juan Gómez de Mora in 1636 , commissioned by King Philip IV .
The first extension to the building was completed in 1537 and was commissioned by King Charles I. Its exterior was constructed by the architect `` Juan Gómez de Mora '' in 1636 , commissioned by King Philip IV .