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To find out, we're going to use what's called sonic echo testing
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Secrets of the Underground

To find out, we're going to usewhat's called sonic echo testing

To find out, we're going to use
what's called sonic echo testing

Full Transcript

00:00:01.000 --> 00:00:05.000
To find out, we're going to use what's called sonic echo testing.
Duration
5 seconds
Views
16
Timestamp in Movie
00:17:58
Uploaded
Jul 08, 2025
Season
1
Episode
2
Genres
documentary

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Movie Summary

Using cutting-edge technologies such as ground penetrating radar (GPR), LIDAR (Light Detection and Ranging), and 3-D imaging, scientists research fascinating underworlds of secret tunnel networks, ancient structures, and bizarre g...
S01 • E01 Each modest-looking home had a bathtub - Secrets of the Underground 00:05
Each modest-looking home had a bathtub
S01 • E02 By sending a sound wave into the wall and reading the echo, - Secrets of the Underground 00:09
By sending a sound wave into the wall and reading the echo,
S01 • E08 This is exactly what I've been looking for, - Secrets of the Underground 00:07
This is exactly what I've been looking for,
S01 • E01 The tunnels linked up with the public sewage system, - Secrets of the Underground 00:15
The tunnels linked up with the public sewage system,
S01 • E03 They're Catholic and this is, you know, - Secrets of the Underground 00:07
They're Catholic and this is, you know,
S01 • E07 And one of the most troubling Areas insar has pinpointed. - Secrets of the Underground 00:04
And one of the most troubling Areas insar has pinpointed.
S01 • E08 Let's see. So, what we've been doing is digitising the maps. - Secrets of the Underground 00:04
Let's see. So, what we've been doing is digitising...
S01 • E07 Happens to be very close To mammoth lakes. - Secrets of the Underground 00:04
Happens to be very close To mammoth lakes.
S01 • E02 So, we have the mallet. We're gonna bang the wall, - Secrets of the Underground 00:10
So, we have the mallet. We're gonna bang the wall,
S01 • E03 But was mere intolerance enough of a motivation for mass murder? - Secrets of the Underground 00:05
But was mere intolerance enough of a motivation for mass mur...
S01 • E08 That way we were able to overlay all of them on top of each other - Secrets of the Underground 00:07
That way we were able to overlay all of them on top of each ...
S01 • E07 Wow, look at that. Resurgent dome, - Secrets of the Underground 00:05
Wow, look at that. Resurgent dome,
S01 • E01 In 2013, the Chicago Crime Commission named Guzman Public Enemy No.1. - Secrets of the Underground 00:07
In 2013, the Chicago Crime Commission named Guzman Public En...
S01 • E08 The main cellblock, the rumoured site of the Spanish tunnels, - Secrets of the Underground 00:08
The main cellblock, the rumoured site of the Spanish tunnels...
S01 • E03 Piecing together the evidence from the recovered remains and historical records, - Secrets of the Underground 00:08
Piecing together the evidence from the recovered remains and...
S01 • E07 There is something underneath it That's pushing it upwards. - Secrets of the Underground 00:04
There is something underneath it That's pushing it upwa...
S01 • E08 But Peter thinks the key to understanding the anomalies we've found - Secrets of the Underground 00:09
But Peter thinks the key to understanding the anomalies we&#...
S01 • E07 Yeah, it's close to a meter Over the last 20 or 30 years. - Secrets of the Underground 00:04
Yeah, it's close to a meter Over the last 20 or 30 year...
S01 • E02 Just one knock is all it takes - Secrets of the Underground 00:06
Just one knock is all it takes
S01 • E03 When a cholera epidemic swept through their camp, - Secrets of the Underground 00:14
When a cholera epidemic swept through their camp,