Complex sentence: Following the alterations carried out by Weld Blundell in the 19th century, the portico of the Pantheon became the new main entrance, and when the house was converted into a nursing home, a new entrance was created at the rear.
Split into simpler sentences: Following the alterations carried out by Weld Blundell in the 19th century, the portico of the Pantheon became the new main entrance. When the house was converted into a nursing home, a new entrance was created at the rear.