Depart London in the morning, and then travel across country by bus to visit the historic port city of Cardiff, capital of Wales since 1955. Take a sightseeing bus tour on arrival to admire the impressive monuments of the city center, where highlights include the new National Assembly building in the regenerated waterfront district of Cardiff Bay. Get some free time for lunch before traveling to historic Caerphilly Castle, famous for having the most elaborate water defenses in Britain. Get some free time to explore the medieval grounds, and marvel at the impressive gatehouses and other architectural features of the 13th-century monument. Depart in the early evening for the scenic drive back to London through the Welsh Valleys and get dropped off in central London in the evening.