Every morning at 9am a military guard escorts the keys to the Tower and the its huge wooden doors yawn open again for outsiders. It’s the most famous castle in the world, a UNESCO World Heritage Site, and a symbol of not just London, but also of a millennium of English history. Less a tower than a fortified minitown of stone and timber, its history could fill this book. Suffice it to say that its oldest building, the four-cornered White Tower, went up in 1078 and the compound that grew around it has served as a palace, prison, treasury, mint, armory, zoo, and now, a lovingly maintained tourist attraction that no visitor should neglect. It’s at the very heart of English history, and exploring its sprawl should take between 3 and 5 hours.

Tickets are sold outside the battlements. Hit the Welcome Centre, just past the Ticket Office, and grab a copy of the free “Daily Programme,” which runs down the times and places of all the free talks, temporary exhibitions, and mini performances. Plenty are offered—the Tower at times feels more like a theme park than a living museum with 1,000 years of history behind it. The prime excursion is the Yeoman Warder’s Tour, led with theatrical aplomb by one of the Beefeaters who live in the Tower (there are about 100 residents, including families, but only one Beefeater, Moira Cameron, is female) and preserve it. Those leave every 30 minutes from just inside the portcullis in the Middle Tower. They’re engaging, but juvenile—expect bellowing and histrionics, each recites an identical script with a gleeful fetish for yarns about beheadings and torture. (In truth, you can count the people executed inside the Tower on your fingers and toes; it was considered an honor to be killed here, since it was private.) For reasons I’m about to explain, I suggest you double back and join the tour later in the day. If you’d like your history delivered without vaudevillian shenanigans, head to the gift shop on the right after Middle Tower and grab an audio tour (£4, but do it early; headsets run out). The official guidebooks (£5) here are pretty good, and they certainly help with orientation.

The key to touring the Tower is to arrive close to opening. At 9am, there’s a short ceremony during which guards unlock the gates for the day. Make a beeline for the two-star attractions since intimidating queues form by lunch: the Crown Jewels, in the Waterloo Block at the north wall (farthest from the Thames) and the White Tower, in the center.

As you enter the Crown Jewels exhibition, you’ll see archival film of the last time most of the jewels were officially used, at the coronation of Queen Elizabeth in 1952. After passing into a vault, visitors glide via people-movers past cases of glittering, downlit crowns, scepters, and orbs worn (awkwardly—they’re 2.3kg/5 lb. each) by generations of British monarchs. Check out the legendary 105-carat Koh-I-Noor diamond, once the largest in the world, which is fixed to the temple of the Queen Mother’s Crown (1937), along with 2,000 other diamonds; the Indian government has been begging to get the stone back. The 530-carat Cullinan I, the world’s largest cut diamond, tops the Sovereign’s Sceptre with the Cross (1661). The Imperial State Crown, ringed with emeralds, sapphires, and diamonds aplenty, is the one used in the annual State Opening of Parliament. After those come candlesticks that could support the roof of your house, trumpets, swords, and the inevitable traffic jam around the Grand Punch Bowl (1829), an elaborate riot of lions, cherubs, and unicorns that shows what it would look like if punch bowls could go insane. Because Oliver Cromwell liquidated every royal artifact he could get his hands on, everything dates to after the Restoration (the 1660s or later). Clearly, the monarchy has more than made up for the loss.

Touring the four levels of the cavernous White Tower requires much stair-climbing but takes in a wide span of history, including a fine stone chapel, Norman-era fireplaces and toilets, the gleaming Line of Kings collection of the Royal Armoury (even small children can’t help but notice the exaggerated codpiece of King Henry VIII’s intricately etched suit from 1540), and some models depicting the Tower’s evolution (it’s been much altered, but the six smallest arched windows on the White Tower’s south side are original to the 11th century). After you’re finished in here, you’ll have an excellent overview of how the whole complex worked.

Once you’ve got those two areas under your belt, take your time exploring the rest. I suggest a stop in the brick Beauchamp Tower (pronounced “BEECH-um,” 1280), where important political prisoners were held and where you can still glimpse graffiti testifying to their suffering. In front of it on Tower Green is the circular glass memorial designating the Scaffold Site, where the unlucky few (including sitting queens Anne Boleyn and Lady Jane Grey) are said to have lost their heads. In reality, we don’t know exactly where they were killed, but Queen Victoria wanted a commemorative site set, and because of the obvious dangers of displeasing the queen, this spot was chosen.

The St Thomas’s Tower, from the 13th century, is closest to the Thames and re-creates King Edward’s bedchamber with authentic materials. Beneath it, Traitor’s Gate, once called Water Gate, originally was used to ferry prisoners in secret from the Thames. Torture was never a part of English law, but it happened here anyway, and the Bloody Tower was where some of the worst stuff went down. Don’t forget to climb the ramparts for that classic photo of the Tower Bridge. But save the extra quid and skip the Royal Fusiliers Regimental Museum, a dreary hodgepodge of military memorabilia.

Daily at 2:50pm, the guards parade outside the Waterloo Block to the Byward Tower. On Sundays, your admission ticket allows you to attend services at the Chapel Royal of St. Peter ad Vincula, the Tower’s church, at 9:15 or 11am; otherwise, the only way to get in, and to see the marble slab beneath which Boleyn and Grey’s decapitated bodies were entombed, is with a Yeoman Warder’s Tour.