It’s a cold rainy night in the walled city of Cordoba, medieval Spain. Watchmen guard the city, unaware that an entire army of christian soldiers are about to launch a surprise attack. In a single night, they conquer the entire city, bringing the muslim rule to an end. 

All over the land, muslim cities were being conquered and taken over by the christians. But amidst all of this, one city remained unconquered, Granada. 

Thanks to its strategic position and the enormous Alhambra Palace, the city was protected, and it remained untouched for another 200 years.

To this day, the Alhambra Palace still stands as one of the most beautiful pieces of architecture ever made. But as you walk through the luxurious courtyards and hallways, you start to notice something even more special, the water. 

Winding its way through the Alhambra is a mind-blowing network of medieval pipes and channels that carry water to vibrant gardens, thermal baths, and elegant fountains. The engineering required to pull this off was astonishing, and it gave the palace things like underfloor heating, and fountains that could tell the time.

This incredible hydraulic system also kept the palace cool and brought life to the surrounding nature for hundreds of years, and it still works to this day.

Getting water to the Alhambra

When the ruler of Granada commissioned the palace, the engineers had one major problem. The hill was around 200 meters above Granada’s main river, and getting water up to the palace would be a huge challenge. And so, they followed the river 6 kilometers upstream to a point that was considerably higher than the palace.

From here, they dammed the river and started redirecting it down a new channel known as the Royal Canal. With meticulous planning, it navigated its way through the difficult terrain using tunnels and aqueducts, maintaining a very shallow slope, until it arrived just outside the palace. It was a huge amount of work, and provided the palace with a constant supply of water – but this was only the beginning. 

The designers of the palace had big ideas; elegant fountains shooting out jets of water, bathing rooms with showers and underfloor heating, and clocks that were powered by water. All of this required much higher water pressure than the Royal Canal provided. 

Pressurizing the water system

And so, to get around this, the engineers started digging out a large pool in an area much higher than the Alhambra. Below this, the water from the Royal Canal would flow into an underground pipe and collect in a well 60 meters below the pool. At the top of the well, the engineers installed a waterwheel, equipped with buckets that could be turned by an animal. 

This would raise the water up to the surface and fill the storage pool with around 400 cubic meters of water. Having all of this water stored above the palace pressurized the entire system, and at the same time, gave the palace a backup supply of water in times of drought.

From here, the water passed over an aqueduct and into the palace, where things start to get really interesting.

Court of the Lions Fountain

The water would split off into a complex network of carefully designed channels, carrying just the right amount of water to the pools and fountains all around the palace – the most impressive of which was located at the heart of the palace. Built in the 14th century, it featured 12 lions that each shot out a jet of water to show what time of day it was.

In a controlled sequence, the lions would activate hour by hour, until all of them were spouting out water by midday. The system would then reset itself and the process would start again. 

But how was this possible with medieval technology? The large bowl at the center of the fountain had 12 holes placed at very specific heights, each leading to a lion via a series of internal pipes.

These holes were carefully calculated to contain the exact same volume between all of them. A central pipe would fill the bowl at a slow and constant rate, causing the water level to rise and activate the lions one by one. The holes were so precisely calculated and the water supply was so constant that it would take exactly one hour to reach the next hole. 

After 12 hours, the bowl would be full of water and a clever siphon inside the bowl would reset the system naturally. As the water inside the bowl started to rise, so did the water in the siphon. Once it reached the top of the siphon, it would curve and start falling down the drainage pipe.

Siphon device

At this point, a seal was created and no air could get in to replace the falling water. This activated the siphon and the surface tension of the falling water would pull the rest of the water with it. In a matter of seconds, the bowl would drain completely and the process would start again.

The water from the lions would exit via 4 shallow channels in the ground and continue on throughout the palace, eventually reaching another engineering marvel, the thermal baths. This is where the kings and diplomats would come to relax and make deals. It featured a cold plunge pool, a hot room with heated flooring and a steam room.

Thermal baths

The water would enter a control room underground and pass through a copper boiler that was heated by burning wood. From here, the hot water would flow through pipes to various fountains and showers around the baths. To provide under floor heating in the hot room, the steam from the boiler was directed through channels underneath the marble floor.

From there, the steam would travel up through pillars in the steam room and exit through small vents, filling the room with water vapor. The roof had a series of star shaped windows that could be opened and closed to control the level of steam.

As the water continued on through the Alhambra’s network of fountains, channels and pools it had another benefit, cooling. Granada is an extremely hot part of Spain, but as the warm air blew over the pools and fountains, the water would evaporate, cooling the air surrounding the palace and making it a very comfortable place to be.

Making water travel uphill

The water continued all the way through the Alhambra until it reached the western portion of the palace, where the soldiers lived. It was built slightly higher than the rest of the palace and so the water had to make a final 6 meter climb to reach it. We saw how waterwheels were used to raise water, but for this section, they came up with something much more impressive.

This was a special device that didn’t require waterwheels, animals or any external power, here’s how it worked.

Water from the system would flow into a container with a hole in the bottom leading down to another container below. As the water traveled down the pipe, a whirlpool would form in the top container. At the center of the whirlpool, a low pressure area would form, sucking air downwards and into the container below. Here, the air and water would mix and this gassy water would be forced into a thin pipe.

The potential energy in both pipes was the same, meaning under normal circumstances, the water pushing down in this pipe would push the water upwards equally in this pipe. But since the water in the thinner pipe was full of air bubbles, it was lighter and could travel higher up the pipe. By passing a constant flow of water through the whirlpool, this device was able to raise water 6 meters higher than when it entered, providing water to the rest of the palace.

Today, many of the clever water systems around the Alhambra still work, and it’s all thanks to the incredible engineers who made them hundreds of years ago.

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