alt.hn

7/22/2026 at 12:56:54 PM

What's Under Your Feet in New York City?

 https://practical.engineering/blog/2026/7/21/whats-under-your-feet-in-new-york-city

by sohkamyung

7/26/2026 at 3:47:48 PM

That's where the mutants live. Also, there's a thousand year old, old New York City buried underneath that had bathroom booths with phones in them.

by mike_hock

7/26/2026 at 9:23:22 PM

Don't touch the weird pink goo you find down there either.

And if your name is Winston, it's just best if you stay above ground, or stick to the subway system.

by hinkley

7/26/2026 at 6:57:08 PM

And those weird booths that look like suicide booths, are no suicide booths. I love you, meatbags! Hello, it’s me, Bender Rodriguez!

by throw1234567891

7/26/2026 at 9:20:12 PM

I guess a robot would have to be crazy to be a folk singer...

by hinkley

7/26/2026 at 7:07:04 PM

Argelio

by argelio4321

7/26/2026 at 9:24:59 PM

So many Ghostbusters II flashbacks watching this.

by hinkley

7/26/2026 at 7:21:40 PM

This is quite informative and useful as I live in NYC. I think in the video he mentioned that the city is collecting all that data on what’s underground to collect all in a database and make repairs easier - anyone know if such data is or will be public, like on data.ny.gov ? And what I’m getting at, is it would be really cool to have this kind of 3d visualization like in the video, but based on actual real data so I could view what’s actually underneath the streets I walk every day.

by radicality

7/26/2026 at 9:20:49 PM

You might run into "security thru obscurity".

by euroderf

7/26/2026 at 2:54:01 PM

https://en.wikipedia.org/wiki/New_York_City_synagogue_tunnel...

by hotstickyballs

7/26/2026 at 3:09:58 PM

Meanwhile in place of power, cable, and phone lines there is a related 18 mile translucent line hung in order to turn the entire city into one big happy home called a *eruv* -- following the law of the highest of high courts to the letter. [0]

[0] https://www.youtube.com/watch?v=hSldb9IMDVU

by dataviz1000

7/26/2026 at 3:56:07 PM

AFAIK the eruvim are not dictated by “high courts” (there is no “high court” at all), but are instead constructed and maintained by various Orthodox groups. Not all Orthodox groups agree about their propriety either, so the presence of an eruv doesn’t necessarily mean that it’s recognized.

(Also pedantic, but it’s not the entire city: there’s a Manhattan eruv that covers a large part of Manhattan, while Brooklyn, Queens, and the Bronx have separate smaller eruvim.)

by woodruffw

7/26/2026 at 6:11:22 PM

There's a lot one could say about

> following the law of the highest of high courts to the letter.

but I don't think that "there is no 'high court' at all" is one, for believers.

by randallsquared

7/26/2026 at 6:23:24 PM

[dead]

by woodruffw

7/26/2026 at 7:15:56 PM

I live in nyc, when I first heard of the eruv couldn’t believe they would come up with such elaborate hacks just to ‘technically’ still be following their religious laws! Now if I remember I try and spot it when out.

It also has a status page! https://eruv.nyc/

by radicality

7/26/2026 at 9:25:05 PM

Idk it makes sense to me.

Like a lot of the rules are very fuzzy in their origin. The whole kosher business comes from a passage about "Not boiling a kid in it's mothers milk". I think most people would interpret that much more literally and you couldn't kill a child goat (kid) and boil it in it's mothers milk; and probably also extend it to other animals like cows. But I'd still think that killing a kid and putting a slice on cheese on the meat would be fine.

So if somebody is going to be obtuse with what you can do it seems like it'd be good fun to figure out all the ways around it.

by lesuorac

7/26/2026 at 8:43:52 PM

Somebody posted on HN before about an eruv index, that’s how I found my city had one as well[0]. I assume they got sort of popular around Jewish neighborhoods.

[0]https://eruv-columbus.com/

by frantathefranta

7/26/2026 at 3:31:11 PM

This is a very weird story.

Religious infighting with 2 fundamentalist sects that somehow boiled down to some people digging a tunnel connecting 2 buildings because of... reasons? Like it seems like they thought that if they built the tunnel that'd magically lead to everyone deciding "You know what, this expansion project is a good thing!"

Very bizarre.

Regardless, I'm glad it got shut down before a collapse killed someone.

by cogman10

7/26/2026 at 3:38:17 PM

> Religious infighting with 2 fundamentalist sects that somehow boiled down to some people digging a tunnel connecting 2 buildings because of... reasons?

The very short version is that both groups claim ownership of that building, and one of them wants to expand it significantly. Neither group is allowed to modify the building because of a court order, so the one that wants to modify it did it surreptitiously in an attempt to create facts on the ground that would modify the status quo.

(Obviously none of this is sensible, but the actual reasons are pretty quotidian.)

by woodruffw

7/26/2026 at 4:00:13 PM

It's quite frustrating. The story ends with:

> four defendants refused to accept a plea deal and were set to be tried in April 2025

I can find loads of stories reporting those facts, but I can't find an account of what happened next. Did they change their pleas? Were they tried?

by masfuerte

7/26/2026 at 3:12:55 PM

An illegal tunnel in a densely populated city like that is a bold move.

This was unexpected though:

> stills taken from videos of the synagogue's interior as well as the room leading to the tunnel, which showed a stained mattress and high chair, respectively, fueled antisemitic conspiracy theories

> A USA Today fact-check stated that the stained mattress seen in viral videos had been removed from behind wood paneling of the synagogue rather than from the tunnel itself, undermining online speculation that the mattresses were in the tunnel

by rdtsc

7/26/2026 at 8:52:35 PM

> An illegal tunnel in a densely populated city like that is a bold move.

I'd say it was an utterly braindead move and pretty much everyone involved is lucky to be alive.

There's just so, so much dangerous stuff you can hit below ground - high voltage cables that really, really do not like it if you even nick them, high current cables giving off nasty electromagnetic fields, ordinary low voltage cables whose isolation is already degraded, old water, gas, steam and sewer mains that may or may not burst simply because the only thing holding together the rust is the pressure from the soil, other, maybe long forgotten tunnels...

And that's before even getting into the issue of potentially getting caved in, creating a sinkhole or an ingress avenue for stormwater.

by mschuster91

7/26/2026 at 7:26:11 PM

This is fantastic, but I so hoped it would come with an infographic of NY's underworld, slice of cake style. I recall seeing one somewhere, but my attempts at finding it again all failed.

by theletterf

7/26/2026 at 8:31:02 PM

The video does have something like that, it's not labeled though, rather he goes through each part and highlights the part he's talking about

by ozyschmozy

7/26/2026 at 6:10:24 PM

One of the most informative videos from Practical Engineering channel. I thought I knew NYC infra fairly well, but I learned so much from that video still (like how NYC's electric grid is actually a grid and more fault tolerant).

by programmertote

7/26/2026 at 7:29:32 PM

Pieces of Belgian cities?

by barrenko

7/26/2026 at 4:31:53 PM

Fascinating. Anything that grows up above ground has a proportionate growth below ground as well.

by zkmon

7/26/2026 at 2:27:32 PM

[dead]

by VoodooJuJu

7/26/2026 at 3:31:53 PM

[dead]

by dfaoidsoi