sentences:  After purchasing the estate Nixon made a number of alterations to the original home, done for both personal preferences and for the needs of the Secret Service.The tennis court was replaced with a swimming pool and much of the estate was wrapped by a 1500-foot C-shaped wall.Today the almost six-acre estate includes about 9,000 square feet of living space, with tile and hardwood flooring, arched doorways and detailed groin-vaulted ceilings.