Sixteenth century Prague was smaller than it is today. Prague Castle was the only part of the city north of the river. The neighbourhood which is now known as Prague 7, or Holešovice, was not inhabited at the time. The Kings used to hunt and fish here. This article is about the tunnel under Prague 7.

It was a sunny but not too warm Spring day as I walked along the embankment which marks the southern border of Prague 7. To my left, cruise boats chugged their way along the river; to my right, the incessant traffic trundled past. I had earlier read something interesting about Stromovka park and wanted to investigate.

The grand park called Stromovka is what’s left of the royal hunting grounds¹. Today it is a 90 hectare green space in Prague. On the weekends it is full of joggers, cyclists, families, and picnic-scoffing groups. People enjoy walking alongside the river which borders the park to the north. In those days, it was part of the royal hunting grounds.

Rudolf II wanted to develop the area. He wanted to enlarge the ponds to keep fish like trout, and he wanted a hunting lodge he could use when hunting game in the area. He asked his Chief Inspector of Mines to sort this out for him. Lazarus Ercker² wasn’t sure how to do this since the existing ponds were stand-alone ponds at the time.

He hit upon an ingenious way of tackling the problem. He knew that the Vltava river flows from south to north, so the river is higher further south than it is along the northern border of the Park. Wouldn’t it be possible, he thought, to let gravity pull water into the park if there were a tunnel to let water in? He designed an adit, a horizontal tunnel³ that burrowed through the neighbourhood into Stromovka.

I stepped off the main road and on to a small grassy part of the embankment which is hidden from drivers’ view. Slightly the worse for wear, and in need of a clean up, was the entrance to the service tunnel for Rudolf’s adit. To its right, forgotten, forlorn and graffitied is the Chief Inspector’s hut. This would be the place where someone would care for the tunnel. Perhaps they could also control the flow of water.

It took 10 years to build, but the Chief Inspector finished his adit on 17 July 1593. He tunnelled underneath what is now Letna park exiting in Stromovka park.

This is quite close to Stalin’s lost statue.

Considering this is before dynamite was invented, this construction project is a feat of engineering and patience.

It’s about a kilometre long, varies between 2 and 4 metres in height and between 90 and 150 cm in width. The difference between the upper level, by the river, and the lower level, by the pond, is 110 cm. Water from the Vltava river feeds the ponds in the royal park this way, and is one reason why they call the larger pond Rudolf’s pond.

I crossed the main road and climbed the incline into Letna Park. A few ventilation ducts are still visible in the neighbourhood and I wanted to look for them on my way to Stromovka. After zigzagging along the steep path, I caught my breath by the first one. It almost looks like one of those old World War II military pill boxes.

Miners used these shafts to haul out stone and debris from the excavation works underground⁴. In the tunnels, miners would insert heated iron rods to raise their temperature, and then throw cold water over the rock to make it shatter⁴.

I made a beeline for Stromovka. I wondered what the built-up district looked like as a hunting ground. The only hunting you find these days is for the latest hipster coffee shop. Half-way through Čechova street I found the second ventilation shaft. Looking like a decrepit TARDIS, this dates back to 1906⁴ it squats along the tree-lined street. There’s no sign to show what it was, or what it does.

Ten minutes later, I watched as a two-carriage train tootled through a raised set of tracks in Stromovka park. I sauntered down to the other side of the adit. The control room, with a rushing sound of water echoing throughout its interior, is as graffitied as its twin by the river. The exit of the maintenance tunnel nestles amidst the greenery, marked only by a stylish letter R on the keystone.

Behind me, the ponds of Stromovka park stretched out. Around me, children swatted bees from their ice-creams and couples laughed in the Czech spring sun. Who knew this park would have been so different had Lazarus Ercker not been so ingenious? Who knew there was a hidden tunnel under Prague 7?

Do you know of any river-fed ponds? Leave a comment below to tell us about them!

1. Royal Game Reserve – Stromovka; Prague.EU; (Retrieved 2018-05-19) [↩]
2. Lazarus Ercker; Richard S Westfall; The Galileo Project; (Retrieved 2018-05-19) [↩]
3. Adit; Encyclopaedia Britannica; (Retrieved 2015-05-19) [↩]
4. Emperor Rudolf II’s tunnel brings the Vltava to Stromovka; Raymond Johnston; Expats.cz; 2020-02-21[↩][↩][↩]