La Lonja de la Seda, also known as the Silk Exchange, is a UNESCO World Heritage site and a masterpiece of Gothic architecture. Built in the 15th century, it served as a trading center for silk merchants. The building features stunning details, including intricate carvings, vaulted ceilings, and a beautiful courtyard. Visitors can explore the various rooms, admire the architectural beauty, and learn about the history of Valencia's silk trade.