Systems that propel cylindrical containers through networks of tubes by compressed air or by partial vacuums, pneumatic tubes are pretty cool to look at. Long a staple of mail rooms, you can also get your food delivered by pneumatic tubes - at least at Christchurch's C1 Espresso. It's a pretty mesmerising process to watch.
Trans-Alaskan Pipeline System and Trans-Mediterranean Pipeline
Environmental concerns aside, the 1,300-kilometre Trans-Alaskan Pipeline and the 2,475-kilometre Trans-Mediterranean (Transmed, built to transport natural gas from Algeria to Italy via Tunisia and Sicily) are impressive engineering feats. Although they each cost the equivalent of billions of dollars to construct, they have provided many times that in terms of economic benefits as a result of crude oil and natural gas deliveries.
But those environmental concerns...
London sewer system
Following a severe outbreak of cholera and other preventable diseases in the 1850s, city officials set about building a modern sewerage system. Reinforcing the pipe walls with what was - at the time - considered an innovation in Portland cement, the system was also built to accommodate future city growth. Of course, more than 150 years later it's in need of repair and expansion to accommodate a metropolitan area with a population of millions of people, but that it's lasted as long as it has is pretty impressive.
The Romans built numerous aqueducts throughout their vast empire. More than 2,000 years later, many of them are still in use.
Sherlock Holmes' pipe
Even if you don't smoke or don't have a particular fondness for pipes, you have to admit this looks pretty cool. The perfect accessory to any outfit. Or at least it would be if smoking wasn't so bad for you.
Few things are as impressive to hear as a large pipe organ in a cathedral. And surprise, surprise: there's some pretty amazing engineering behind the massive instruments.
Opened in 1994, the Channel Tunnel is considered an engineering marvel - not the least of which is because it links Britain with continental Europe for the first time in thousands of years. Oh, and it also boasts the longest undersea portion of any tunnel in the world.
Optical fibre pipes
Optical fibres can transmit incredible amounts of information at incredible speeds. Unfortunately, they're also kind of fragile. So what do you use to keep them protected? That's right: pipes! And they can be used for astoundingly harsh environments, like the extreme pressure in the freezing depths at the bottom of the ocean.
Everyone's favourite red overall-wearing cartoon plumber has been going down pipes for more than 30 years now with his brother Luigi. He does it so well, let's be real and admit it's one of the first things we think of when we think of pipes.
The US Air Force is able to refuel its planes in midair using aircraft such as the KC-135 Stratotanker - allowing missions such as fighter jets taking off from bases in the US, flying to Syria or Afghanistan to bomb ISIS or Al Qaeda targets, and then flying back to the US without ever touching the ground. But when both the plane being refuelled and the plane supplying the fuel are flying at thousands of kilometres per hour in temperatures far below zero and at extreme altitudes far higher than commercial aircraft usually fly, it takes a pretty well-designed pipe to help make sure nothing goes wrong.
Pipes for snowboarding
Let's be honest: shredding powder wouldn't be the same without them.
Dame Kiri Te Kanawa