A great love of nature led Dr. Charles Horace Mayo, co-founder of the Mayo Clinic, and his wife Edith (Graham) Mayo to purchase a small red brick house and 340 acres in 1907. Their growing family and desire to preserve the natural beauty of the surrounding woodlands led to the construction of two more houses and the accumulation of 3,300 acres. Ivy Lodge was built in 1908, and in 1910 Dr. Charlie himself designed and built the Big House on the hillside. Unique in construction, the Big House reflects a variety of architectural styles and ideas gathered by the Mayos in their world travels. It is built of poured reinforced concrete, with outside walls over a foot thick enclosing an air space of hollow insulating tiles. Nevertheless it remains homelike rather than monumental. Antiques and art treasures blend in an atmosphere of informality and hospitality. Ease of circulation and ample lighting through long rows of windows and large bays are among the additions made by Dr. and Mrs. Charles William Mayo, the second occupants. Many notables, including President Franklin D. Roosevelt, Emperor Haile Selassie of Ethiopia, and the King and Queen of Nepal, have been entertained here. In addition to its houses, the estate has a summer teahouse, a greenhouse, stables, and barns.