I’m a Londoner who always rides the Tube. Here are 10 features of the Underground that would surprise most Americans.

Only about 31% of trains on the Tube network have passenger air conditioning, according to Transport for London (TFL). As soon as a heat wave hits, I cannot ride the Tube without carrying blotting paper and a handheld fan.

Some lines are notorious for how hot they get. Having to take the Central Line in the summer will elicit sympathy from any Londoner. The London Standard reported that it reached almost 103 degrees during the recent June heat wave.

With that in mind, you may also be surprised to learn that in 1926, the London Underground was advertised as “cooler below” on a hot day.

Unlike the hard plastic seats in most American public transport, Tube seats are covered in a woolen fabric called moquette.

It’s been used on the Tube since 1920 because it hides wear and tear and dirt, and also because it’s durable.

Admittedly, it does gross me out a bit, even though it gets cleaned. But it’s definitely more comfortable than plastic, at least.

While the New York City subway has a flat fare, the cost of a journey on the Tube varies depending on how far you travel.

London’s transport network is split into fare zones, from the most central to the farthest out: Zones 1 to 9. People here often joke that the zone you live in also determines how much of a “true” Londoner you are.

For example, a single journey within Zone 1 will cost you £3 at off-peak hours, and £3.10 at peak hours. However, if you travel from Zone 6 to 1, or vice versa, it will cost you between £4 and £5.90.

Rush hour is known as peak time on the Underground and other rail services.

Peak time is Monday to Friday, except public holidays, between 6:30 a.m. and 9:30 a.m., and between 4 p.m. and 7 p.m. Fares are higher at these times.

In addition to saving a bit of money, I would recommend avoiding these times for travel. Carriages can get crammed, and people can be unforgiving if you’re carrying a large suitcase or walking too slowly.

With all these varying fare prices, you have to tap your card, contactless, Oyster, or physical ticket in and out of the Tube.

Often, there are barriers upon both entry and exit, so you wouldn’t miss this, but sometimes there aren’t. In these stations, you have to look for a yellow card reader to tap out.

If you don’t tap out, you will be charged the maximum fare for that line. I’ve had this happen to me before, but luckily, you can request a refund from TFL if it happens again.

If you like your personal space, you might be pleased to know that most Tube carriages have an armrest between seats.

However, despite their name, I see them as more of a separation barrier than an actual armrest. Resting your arms on these is a faux pas (unless you absolutely have to) if there are people sitting on either side of you.

While you may be expecting to descend deep underground when taking the Tube, this isn’t always the case. Despite its name, most of the London Underground’s stations are above ground. I find this is handy for getting service.

The Waterloo & City and Victoria lines are the only two fully underground tube lines.

My ultimate word of advice for anyone coming to London is to never stand on the left-hand side of the escalator. The left side is for people walking up or down in a hurry.

It’s an efficient system that has saved me from being late hundreds of times. You will be asked to move aside if you break this rule.

If you like all things spooky and historical, I recommend checking out the London Transport Museum, which offers tours of disused Tube stations, passenger corridors, and tunnels.

Some of these spaces have been used as sets for TV shows and films, including Skyfall and Sherlock.

London is not quite the city that never sleeps. I have rarely taken the Tube past midnight and instead rely on Ubers and night buses to get me home.

Only five Tube lines run 24-hour services: Central, Jubilee, Northern (Charing Cross branch), Piccadilly, and Victoria. The Windrush line, which is part of the London Overground, also has a night service.

The Night Tube is also only open on Fridays and Saturdays.