How did Leon Battista Alberti use Classical Roman architecture in his building designs?

Leon Battista Alberti was a pivotal figure in the Renaissance who integrated Classical Roman architecture into his designs through rigorous study, theoretical writing, and practical application. His approach was grounded in the belief that beauty in architecture is a "reasoned harmony" of all parts, a principle he codified in his influential treatise, Ten Books on Architecture.12

Alberti’s use of Classical elements included:

• Classical Orders: He applied the Roman system of orders to building facades. For example, at the Palazzo Rucellai, he superimposed pilasters of different orders—Tuscan, Ionic, and Corinthian—across the stories to establish a logical, proportional relationship.23
• Roman Motifs: He famously adapted the ancient Roman triumphal arch motif. At the Church of Sant'Andrea in Mantua, he utilized this motif to organize both the facade and the interior, creating a rhythmic, monumental space that influenced later architects.13
• Proportional Theory: Inspired by Vitruvius, Alberti emphasized mathematical harmony, ensuring that architectural elements were perfectly measured and integrated, reflecting the classical ideal of order.12