La Lonja de la Seda de Valencia (The Silk Exchange)

A beautiful late-15th-century Gothic building with multiple rooms and gardens, originally a trading hall for the city's silk merchants. The main hall is famous for its towering spiral columns, and the whole site is a UNESCO World Heritage monument. Today it's often used by Spanish royalty and politicians for important gatherings. It's right around the corner from the Central Market, so it's a nice stop before hitting up the market for lunch/provisions.