In the 1920s, Italy was trying to grow its industrial base and to do that, they need electricity.
What better way, they thought, than to build a hydro-electric dam in the Vajont River in northern Italy. It would join the global trend to dam the world's rivers.
With the intervening depression and World War II, nothing happened until 1957 when construction began.
Although dwarfed by the 567-metre Usoi Dam in Tajikistan, it remains one of the world's tallest with a height of 262 metres.
The precipitous Monte Toc valley just above the town of Longarone would be technically challenging.
If the dam was an engineering triumph, it was a geological and human disaster.
It might've helped if they'd taken note of the local name Monte Toc, which roughly translates as "the rotten mountain".
Perched atop an impermeable layer of slippery clay, is a massive slab of limestone. It wasn't long after construction began that the rotten mountain hinted at how it might react to having its feet wet.
Fractures appeared, causing the ground to shift as they built an access road.
If they needed another sign that something was wrong, that arrived in March 1959 with a landslide at the nearby Pontesei Dam.
An estimated 3 million cubic metres fell into the lake, triggering a 20-metre wave that killed one person.
The problems at Lake Vajont grew worse during 1960 with more minor landslides. For "undermining the social order", the Italian government sued journalists who reported what was happening.
Then, in November 1960 when the water approached three-quarters full, a sizeable chunk of Mount Toc collapsed into the lake.
The local geology was obviously an issue, the electricity monopoly SADE running the project paused the filling and initiated a series of experiments using a 1:200 scale model.
Their experiments predicted that a future landslide would cause minimal damage to the reservoir and downstream. They were wrong.
On October 9, 1963, 270 million cubic metres of rock slid down the mountain and into the lake. Like a gorilla jumping into a bathtub, the water sloshed up the other side, then back again.
The tsunami surged 200 metres over the dam and into the valley towards Longarone.
MORE ASK FUZZY:
Fifty million cubic metres of rock, mud and water squeezed through the narrow gorge, creating a shockwave that shattered windows even before the water arrived.
Longarone was devastated with the loss of nearly 2000 lives.
Today, scars on Monte Toc are still visible, and the disaster is one of the best-studied landslides in the world.
The Fuzzy Logic Science Show is at 11am Sundays on 2xx 98.3FM.
Send your questions to AskFuzzy@Zoho.com; Podcast: FuzzyLogicOn2xx.Podbean.com