In towns even most better-off people lived in terraced houses, which typically opened straight onto the street, often with a few steps up to the door. There was often an open space, protected by iron railings, dropping down to the basement level, with a discreet entrance down steps off the street for servants and deliveries; this is known as the "area". This meant that the ground floor front was now removed and protected from the street and encouraged the main reception rooms to move there from the floor above. Where, as often, a new street or set of streets was developed, the road and pavements were raised up, and the gardens or yards behind the houses at a lower level, usually representing the original one.

Answer this question, if possible (if impossible, reply "unanswerable"): What were put behind the house on the same level?
unanswerable