On January 9, 1863, a steam locomotive huffed and puffed out of Paddington station and plunged beneath London's chronically congested streets.
Travelling via the mainline rail hubs of Gower Street (now Euston Square) and King's Cross, the train completed its 6km journey at Farringdon, close to the big banks and merchants' headquarters of the City of London, the financial hub of the British Empire.
This was the world's first-ever subterranean rail trip - the culmination of eight years of planning, lobbying, financial and engineering headaches and the toil of more than 2000 navvies.
Drawing 40,000 passengers on its first full day, the Metropolitan Railway was also the maiden cog in what would become the planet's most famous underground rail network.
Today, as the Tube toasts its 150th anniversary with special events and exhibitions, including heritage steam train rides, I'm indulging my inner trainspotter and retracing some of that first route.
Dubbed "the train in the drains", the Metropolitan Railway no longer exists in its original form, so I must catch the Tube's Hammersmith & City service from platform 16 at Paddington - a drab spot on the station's northern edges which exudes none of the majesty of the main terminus, a domineering iron- and-glass train shed, designed in 1854 by Isambard Kingdom Brunel.
As the train rattles underground, gently swaying from side to side, silent passengers twiddle with their smart phones and leaf through newspapers and books.
Then we stop at Baker Street and it's as if a magical porthole into Victorian London has appeared.
One of the original stations serving the Metropolitan Railway, Baker Street station is now a mind-boggling maze at the confluence of five Tube lines (there are 11 in total, centrally managed by Transport for London).
Yet the Hammersmith & City line platform oozes antiquity: nestled in a gloomily lit brick arched tunnel, it is lined by wooden benches stamped with black and white Baker Street signs, and brick walls studded with old photographs and iron plaques embossed with "Metropolitan Railway 1863".
On a cool, winter's night, it's easy to imagine Sherlock Holmes, deerstalking cap on, ambling down the platform, puffing away on his pipe. Sir Arthur Conan Doyle's fictional character lived at 221b Baker Street and Holmes' pipe- smoking silhouette decorates some of the station's tiled walls.
Baker Street's atmosphere was heightened last month, when a restored, coal-fired, steam-billowing locomotive built in 1898 chugged in on one of a clutch of heritage rides to celebrate the Tube's 150th anniversary. It was the first underground steam passenger journey in central London since the network was completely electrified in 1905.
Fares as steep as $275 (£180) didn't deter passengers, with seats on the gas-lit wooden carriages - split into first and standard classes, as in the olden days - sold out within hours of tickets being released.
The old trains will be in action at various times this year, notably May 25-27, a weekend dubbed "Steam back on the Met". Several other events are marking the anniversary, including shows at the disused Aldwych station.
Founded in 1907 as Strand station, Aldwych was used as a bunker during the two world wars. Its supposedly haunted tunnels and shafts have appeared in British movies like V for Vendetta, Atonement and 28 Weeks Later.
Close by, at the heart of Covent Garden, the London Transport Museum is a must for Tube fans.
Housed in a striking iron-and-glass Victorian building (a former flower market), the museum displays a sparkling array of classic modes of transport that have ferried Londoners from A to B: horse-drawn omnibuses, electric street trams, red double-decker buses, shiny black cabs, steam locomotives and a Tube carriage circa 1938.
Other displays detail the technical and engineering aspects of the Tube's birth, which was hailed as "the most stupendous engineering undertaking yet achieved in the railway world" and provided the inspiration for other subterranean transport networks.
The museum also has accounts of what it was like to travel on the Tube before electrification: an 1884 Times newspaper editorial decries a smoke- filled trip from King's Cross to Baker Street as "a form of mild torture which no person would undergo if he could conveniently help it".
Of the museum's eye-catching multimedia attractions, I'm drawn to a digital screen showing the evolution of the Tube map, year-by- year, revealing how lines and stations have appeared and disappeared.
The longest line is the Central (red) line. The longest journey you can make on the Tube without changing is the stretch between West Ruislip and Epping (89 minutes when there are no delays). The furthest Tube station from central London is Chesham - 40km north-west of Charing Cross as the crow flies.
Another of the museum's zones flaunts vintage Underground roundels (a red circle crossed by a horizontal blue bar), mini models of notable stations (from the Art Deco glory of Charles Holden's Arnos Grove to the gleaming futurism of Sir Norman Foster's Canary Wharf), and colourful posters advertising the Tube's attempts to "Keep London Moving".
The best of the museum's 3300 archive posters is being showcased in a special exhibition, Poster Art 150, until October 22. Replica posters can be purchased in a museum gift shop jam-packed with souvenirs.
On sale there is Underground: How the Tube Shaped London. This superbly illustrated coffee-table tome marks the 150th anniversary and investigates how the venerable network not only tunnelled through London's soft bed of clay, but also became a global cultural icon.
As Peter Hendy, Transport for London commissioner, writes in the book's introduction: "Today it is impossible to imagine one without the other. London and its underground are indivisible."
London Transport Museum is at Covent Garden Piazza. Admission is $23 for adults. Tickets provide unlimited museum entry for 12 months. Under-16s are free. ltmuseum.co.uk
Transport for London provides information on Tube fares, maps, timetables and service updates. tfl.gov.uk
Single fares on the Tube are expensive (from $6.90 a ride), so if you're planning to use the Tube regularly, get an Oyster card. Available from all station ticket offices (for a $7.60 refundable deposit), it runs on a pre-paid top-up basis, with Oyster users enjoying discounted fares.
If you'd prefer to buy in advance of your trip, see visitbritainshop.com/australia/travel-transport.html.