In Beijing's historic city center, it is against the law to erect anything higher than three stories. The rule harks back to imperial times, when no structure was permitted to be taller than the Drum Tower, whose drums marked the hours of the emperor's day. The emperor is long gone, but the Forbidden City, the seat of power during much of the Ming (1368-1644) and Qing (1644-1911) dynasties, remains a carefully preserved 178-acre sprawl of palaces, courtyards, gardens, reflecting pools, houses, theaters, dining halls, offices, gates, and alleyways, surrounded by a moat in central Beijing. Named for its fortress-like seclusion from all but royals and those who served them, the city's 9,000 rooms housed the royal family, eunuchs, concubines, guards, and servants. Sometimes now when the place is teeming with visitors, it can feel like they're all back. Yet insiders know that when the crowds are low, the Forbidden City is an ideal place to contemplate the dynamic present against a haunting past.