1. Ride the subterranean Mail Rail
After standing in somebody's armpit on the Tube – London's overheated, overpopulated transport network – the last thing you'll want to do is pay to go back underground.
However, the Mail Rail isn't your typical tube experience. Between 1927 and 2003, the Post Office's underground micro-railway carried millions of letters a day on a 6.5-mile network beneath the streets of London.
The tracks have lain disused for over a decade, but in September 2017 the Postal Museum reopened the Mail Rail to the public, allowing visitors to board replica rail cars and ride through this once forgotten piece of the city's heritage.
2. Go kayaking on the Thames
The guys at Secret Adventures describe themselves as follows: "we like water, we like fire and we like to explore". In their night-kayak-across-London experience (£55), they embrace the former and the latter.
Organised to coincide with the falling tide, you set sail from the beach at Vauxhall Bridge Road (yeah, London has mini-beaches) eastwards towards Greenwich.
There are many ways to glimpse the city's blockbuster sights, like the Houses of Parliament, St Paul's Cathedral and Tower Bridge, but none is more romantic or invigorating than with the slosh of the Thames beneath you.
Katherine Futers/Secret Adventures
3. Experience the surreal House of Dreams
Kitsch, multicoloured, eccentric. Visiting the House of Dreams is unlike any other experience in London.
The life's work of artist Stephen Wright is a surreal and overwhelming collection of plastic dolls, bleach bottles, Christmas decorations and vinyl records, taking up every inch of his Victorian East Dulwich home.
Wright became a follower of outsider art, the movement that eschews what is "tasteful" and "acceptable", after becoming disillusioned with mainstream art and textiles after a lifelong career in design.
The House of Dreams is only open on certain days and by appointment, so check before you go.
Michael Vaughan/House of Dreams
4. Go for a walk in the woods
Back in the day, the Great North Wood sprawled all the way from the Thames to Croydon. While most of this has been lost to development over the centuries, the enchanting neighbouring Sydenham Hill and Dulwich woods are the closest ancient woods to central London.
Embrace the labyrinth of tall trees and don't worry about trying to figure out where you are. Part of the joy of the woods is the birdlife; keep an eye out for green parakeets, woodpeckers, tawny owls and sparrowhawk.
5. Sleep with the lions
Since May 2016, visitors to London Zoo have been able to take their zoological obsessions to the next level.
The Gir Lion Lodge contains nine brightly coloured cabins, allowing visitors to sleep at London Zoo just a matter of meters away from a pack of Asiatic lions.
Why settle for the roar of a runway or a busy central London street, when you can have the guttural roar of a big cat waking you up in the morning?
6. Walk beneath the Thames
There are 33 bridges across the Thames in London, from Richmond to the estuary and beyond. However, our favourite way to cross the Thames is via the Greenwich and (lesser-known) Woolwich foot tunnels.
Each marked by cylindrical brick entrances, the ones in Greenwich being opulently domed, these pedestrian tunnels were opened in the early 20th century to provide easy access to the city's northern docks for those who lived south of the river.
Today, millions of people still walk these atmospheric tunnels, which are free to use and have spiral staircases and lifts at each end.
7. Go zip wiring on the South Bank
The biggest, fastest, inner-city zip wire landed on London's South Bank in 2017.
Based in Archbishop's Park in Lambeth, the zip wire hurtles you at a speed of up to 50 miles per hour, bringing blurry views of the London Eye and Westminster Abbey in the distance.
If you're interested, you'll have to act quickly: the thrill-seekers at ZipWorld will be zipping up their suitcases and taking their business elsewhere after October 1 2017.
8. Go on a cryptic treasure hunt
If you want to see a hidden side of London, but without following a tour guide holding a Union Jack umbrella, Hidden City might be the solution you're after.
Their London hunts range from the Sherlock Holmes-themed "Moriarty's Game" to the Snow White-inspired "Enchanted Mirror", or shorter hunts around Shoreditch and Covent Garden.
All you need is a few mates, a phone full of battery and a penchant for cryptic clues.
Inspired? Our very own podcast, The Rough Guide to Everywhere, will be digging beneath the capital's surface in a live episode at the London Podcast festival. Book your tickets now.
Header image: Pixabay/CC0