Built by Shah Jahan, the most prolific architect and builder of the Mughal empire, Lal Qila must have been a very modern departure from labyrinthine Agra Fort (which is older but a great deal better preserved and atmospheric). It was the seat of Mughal power from 1639 to 1857. Named after the red sandstone used in its construction, Red Fort covers an area of almost 2km (1 1/4 miles). Visitors enter via three-story Lahore Gate, one of six impressive gateways. You'll pass through Chatta Chowk, which has quaint shops selling cheap souvenirs (some rather nice handbags). You'll arrive at Naqqar Khana, where the emperor's musicians used to play. From here you look up into Diwan-I-Am, the 60-pillared "hall of public audience," from where Emperor Shah Jahan used to listen to his subjects' queries and complaints as he sat cross-legged upon the beautifully carved throne (an age-old custom that his despotic son, Aurangzeb, who cared little for his subjects, discontinued). Behind this lie Rang Mahal, the royal quarters of the wives and mistresses, and Mumtaz Mahal, probably used by a favored wife or by Princess Jahanara, who evoked such envy in her sister's heart. Next up are Khas Mahal, which housed the emperor's personal quarters (he would greet his subjects across the Yamuna River from the balcony); gilded Diwan-I-Khas, where the emperor would hold court with his inner circle from the famous jewel-encrusted Peacock Throne (taken by Persian invader Nadir Shah in 1739 and still in Iran); and finally the Hamams, or royal baths, whose fountains of rose-scented water would give modern-day spas a run for their money. In front of the hamams is Moti Masjid, built by Aurangzeb exclusively for his own use -- a far cry from the huge Jama Masjid his father built in order to celebrate the faith together with thousands of his subjects.
A few examples of beautiful carving, inlay, and gilding remain, particularly in Diwan-I-Khas, but after so many years of successive plunder it takes some contemplation (and a guide) to imagine just how plush and glorious the palaces and gardens must have been in their heyday; they were ruined when the British ripped up the gardens and built their ugly barracks (the fort is incidentally still a military stronghold, with much of it off-limits). Consider hiring a guide at the entrance, but negotiate the fee upfront and don't expect much by way of dialogue (guides often speak English by rote and don't understand queries); do expect to be hassled for more money. If you're staying in an upmarket hotel, arrange a guide through the concierge.