To the countless fans of Sherlock Holmes, his fictional exploits are as real as 221B Baker St., the Langham Hotel, Charing Cross Station, the Lyceum Theater and one Holmesian landmark after another in London.

If you can remember no other Holmesian landmark, you do remember 221B Baker St., the address of the flat Holmes and Dr. John Watson shared.

Stroll north from the Baker Street Underground station and where 221B should be is a disappointing office building.

But don’t give up. Continue north a few doors to a narrow Victorian-looking row house where you’ll find the “re-created” rooms of Holmes and Watson. For £8 admission (£5 for children), you can climb the stairs and take your time examining Holmes’ bedroom and the parlor where he received his clients.

Students of “the canon” — the original 56 short stories and four novels written by Sir Arthur Conan Doyle — will find little if anything to quarrel with. In one corner is a table holding a dusty mess of test tubes and other laboratory glassware — as if untouched since Holmes retired to the countryside.

A knife impaled on the mantel over the coal-burning fireplace holds his unopened correspondence. A Persian slipper holds his tobacco. A huge patriotic “VR,” for “Victoria Regina,” has been tattooed into one wall with bullets from when Holmes turned the parlor into an indoor firing range.

The maid, no doubt Mrs. Hudson’s great granddaughter, will invite you to have a seat in Holmes’ chair, don his deerstalker cap and pick up his curved pipe while she or a friend takes your picture.

In the Victorian era of Holmes and Watson, 221B Baker St. didn’t exist. Baker Street didn’t extend that far north. In those days, that part of Baker Street was known as York Place.

Sir Arthur’s stories actually placed Holmes’ flat farther south near the intersection of Baker and Blanford streets.

En route, you’ll pass the Sherlock Holmes Hotel. When you get to Blanford, turn left one very short block to Kendall Place, actually an alley extending south from Blanford.

In The Adventure of the Empty House, the infamous Col. Moran entered the rear of one of the houses set between Kendall Place and Baker Street and tried to assassinate Holmes by firing a shot into the window of Holmes’ flat on the opposite side of Baker Street. But, of course, Holmes was too clever. The shot hit a silhouetted wax bust of Holmes, who then leaped out of a darkened recess of the Kendall Place house to capture Moran.

You can go back to look at the buildings along Baker Street, but they are too new for Holmes’ flat. The Victorian-era buildings were destroyed in the Blitz during World War II.

A couple of blocks farther south on Baker Street, at Portman Square, turn, turn left on Fitzhardinge for two blocks to Manchester Square. Take Hinde Street east from the square until it forms a T with Welbeck Street. Go north one short block to Queen Anne Street, then east again. It is along this three-block-long street Watson lived after wedding Mary Morstan.

Follow Queen Anne Street as it bends to the right and becomes Chandos, then take a left on Portland Place and follow it one block to the Langham Hotel. Built in 1864, it was one of London’s finest hotels in Holmes’ time and crops up often in Holmes’ adventures. It was here the King of Bohemia stayed under the name Count Von Kramm in A Scandal in Bohemia. And it was from here Miss Morstan’s father, Capt. Arthur Morstan, disappeared.

At the hotel, turn south down Langham, which curves and becomes Regent Street, to the Oxford Circus Underground. Go one stop up the Central Line to the Tottenham Court station. From there, make your way northeast to the British Museum, along the east side of which is Montague Street.

On this street, essentially unchanged from Victorian times, Holmes lived “just around the corner” from the British Museum in 1878.

When Sir Arthur first came to London in 1891 he too lived near here, at 23 Montague Place, the street running along the north side of the museum. To the north of this street is the University of London, where Watson obtained his medical degree.

Now make your way back to the Tottenham Court Road Underground and take the Bakerloo line to the Embankment Underground.

Exit the station to the left onto Villiers Street. It was to a hotel along this short street that Holmes directed his Hansom cabdriver to take him upon arriving in London after college.

As you stroll up Villiers Street, to your left you will see Craven Passage under the arches of Charing Cross Station. At the other end of the passage at Northumberland Street is a pub called “The Sherlock Holmes.”

In Holmes’ day it was the Northumberland Hotel, where Holmes came to meet Sir Henry Baskerville in The Hound of the Baskervilles. On the ground floor, the pub contains several displays of “mementos” of Holmes’ adventures. Sir Henry’s room was on the first floor — Americans would call it the second floor — and there today is Mrs. Hudson’s Restaurant as well as another re-creation of Holmes’ parlor.

Watson reported that he and Holmes had a weakness for Turkish baths. Nearby, at the corner of Craven Passage and Northumberland Avenue, once stood Nevill’s Turkish Bath, where Holmes showed Watson a letter beginning The Illustrious Client.

Back at the other end of Craven Passage, continue up Villiers Street to where it ends at The Strand. On the left you’ll find the Charing Cross Hotel and the entrance to Charing Cross Station.

This is one of the most significant Holmesian landmarks, cited in at least nine of the adventures as a transportation hub or a place from which Holmes posted letters or dispatched telegrams.

It was in the Charing Cross Hotel that Holmes captured the spy Hugo Oberstein in The Adventure of the Bruce-Partington Plans. On the north side of The Strand once stood the Lowther Arcade.

In The Final Problem, Holmes told Watson to meet him on a train at Victoria Station. But to shake anyone who might be following him, he told Watson to take a cab to the south entrance of the arcade, dash through it to the opposite exit on William IV Street, then jump into another waiting cab, driven as it was by a disguised Mycroft Holmes.

Charing Cross Hospital also stood across the street from the station. It was to here Holmes was taken after being assaulted at the Cafe Royal in The Illustrious Client.

Go east along north side of The Strand to the intersection with Southampton. The offices of The Strand magazine, in which many of Holmes’ adventures were originally published, once stood here.

Three blocks farther along The Strand, take a left on Wellington Street; you will find the Lyceum Theater, now all boarded up. In The Sign of Four, Mary Morstan received a mysterious note instructing her to meet an anonymous friend outside the theater at the third pillar on the left. You can debate whether it’s the third from the left as you face the building or face away.

There are, of course, many other Holmesian landmarks to seek in London, including St. Bartholomew’s Hospital, near St. Paul’s Cathedral. It was at Bart’s, as it is nicknamed, that Watson and Holmes met each other and agreed to share the rooms on Baker Street.

Don’t miss what in Victorian times was called New Scotland Yard, just north up Victoria Embankment from Westminster Bridge.

There are dozens of other Holmesian landmarks to be found around London.

Most can be found by the most amateur detective with a London map. But two-hour walking tour offered by London Walks, whose brochures can be found in any hotel, adds to the fun and makes it far easier.