A block from the Tiber river, and a ten minute walk from the Pantheon, the Spada gallery is a wondrous art collection housed in a 15th century palace (Palazzo Spada) which used to belong to a family of the same name. Walking along Capo di Ferro and looking up at the outer walls of the palace one already begins to see the artwork of the structure — ornate statues of historical Roman leaders perched a few stories above your head. Entrance to the building is cheap, around 5 euro, which is well worth the price to see the beautiful interior.
(Sygic Travel) Sada Gallery
The most famous part of the gallery is probably not the gallery itself, but the courtyard on the ground floor. That portion is the "Galleria Prospettica" designed by Francesco Borromini in the 1600's. The fascinating hallway of Doric pillars ends in a row of bushes with a roman hero looming against the far wall. Closer inspection, however, reveals that the roman statue is only a few feet in height and that it is a trompe l'oeil — an optical illusion by the 17th century artist.
(Rolf Gross) Galleria Spada
However, the real treasure trover of this gallery are the paintings and statuary in the floors and rooms above. This gallery feature art of all shapes and sizes which practically covers the walls and even the ceilings of the amazing halls. The ceilings too feature fascinating designs such as a series of paintings which depict the major continents of the world as goddesses styled after their respective landmass. As can be seen in the photo above, there are also Roman busts, globes, and miniature statuary.
If one has an interest in art, or would like to acquire such an interest, you can do worse than a visit to the Spada gallery. A smaller building than some other more famous sites, it nonetheless makes particularly fantastic use of real estate.