Between 1827 and 1829, Juan Bandini had a U-shaped home built off one corner of the plaza. Compared to most of the other modest adobes, Casa de Bandini was a grand mansion and the social center of town. The rooms had thick, insulating adobe walls. The ceilings were covered on the inside with heavy muslin to trap insects, dirt and straw that fell from the thatch roof.

Construction of the casa was a colossal undertaking. It contains an estimated 10,000 adobes bricks, weighing as much as 60 pounds each. The foundation, made of large round river rocks, rose four and a half feet above ground at the corner facing the plaza. The heavy labor was most likely performed by Christianized Indians hired from the local mission.

Since the building was remolded, interesting paranormal activity has occurred through out the building. One room in particular called the "Isadora Bandini" room. Isadora would use this room when she stayed there to remember her childhood days. A lot of people including the building manager believe that her spirit is still in the room. Investigators have conducted research in this room, and once they started to get activity and ask questions the activity would stop. Until they remembered that Isadora spoke Spanish. When they would ask questions in Spanish, they were able to capture her name on an EVP.

The spirit likes to open the curtains, move the position of the mirror, and put the bathroom robe on the floor. There is also the sound of a cat purring at night.

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Featured on TV's Ghost Adventures, the 1827 building that houses the Cosmopolitan is said to be haunted. It was originally built by Juan Lorenzo Bandini, his young daughter died in the home, and her bed and rocking chair remain in the house. The chair has been known to rock by itself, and a witness reported hearing the unexplained sound of a child crying. Other rumors and mysteries surround the place as well.