Santo Spirito has a very simple and beautifully regular plan, and its interior has a singular charm and grace: over the crossing is raised a low dome. The columns of the arcade are Corinthian columns, and the refinement of their detail and proportions strikes the eye at once on entering the building. The influence of Brunelleschi, who died in 1440, was perpetuated by the works and writings of Alberti (born 1398) an architect of literary cultivation who wrote a systematic treatise which became extremely popular, and helped to form the taste and guide the practice of his contemporaries. He lived till near the close of the fifteenth century, and erected some buildings of great merit. To Alberti we owe the design of the Ruccellai Palace in Florence, a building begun in 1460, and which had been preceded by somewhat bolder and simpler designs. This is a three storey building, but has pilasters carried up the piers between the windows and a regular entablature and cornice[31] at each storey. The building is elegant and graceful, and though the employment of the orders[32] as its decoration gives it a distinctive character, it bears a strong general resemblance to the group of which the Strozzi Palace (Fig. 61) may be taken as the type. The earliest Florentine palaces are the Riccardi, which dates from 1430, and the Pitti of almost the same date; Brunelleschi is said to have been consulted in the design of both, but Michelozzo was the architect. The distinguishing characteristic of the early palaces in this city is solidity, which rises from the fact that they were also fortresses. The Pitti, well known for its picture gallery, is a building of vast extent, built throughout in very boldly rusticated masonry, the joints and projections of the stones being greatly exaggerated. The Riccardi, a square block of building, bears a considerable resemblance to the Strozzi, but is plainer. It is a most dignified building in its effect.