South Korea’s capital offers dazzling modernity blended with reminders of its long history. Visitors cannot miss the N Seoul Tower, the 777-foot spire standing atop Mt. Namsan. Take the cable car to the mountaintop, then reach the observation level 1,574 feet above the city. The city’s stone walls, constructed along hilltop ridges at the end of the 14th Century, are a UNESCO World Heritage Site. …