In 2006, Prague's mayor Pavel Bém, the physician and mountain climber who has been to Mt Everest as well, signed the deal to build the new tunnel called Blanka – which is a female first name (which may also mean a "little membrane" or "maidenhead", when combined with the adjective "virgin").
The tubular tunnel seems to have a decently elegant design, not too dissimilar from the tubular holes in the Prague subway.
As it turned out, the lore says, they gave a female name to the tunnel because the tunnel was getting wet from the bottom – and it was apparently never finished. ;-) I hope that you have correctly understood that there have been humidity problems during the construction – which were threatening some electric cables, too.
Humidity problems are nothing new in similar underground constructions in Prague (and elsewhere?). When the subway was being built in the 1970s, the Soviet engineers were shocked to discover that there was something called the Moldau River above them, too.
The original plan was to open the Blanka Tunnel in 2011. It's 2015 now which means that the delay was 4 years. These days, the construction companies seem to agree that the original deadline wasn't realistic (or at least was very risky, lacking any reserves) and I tend to believe the companies if there is some consensus among those. Most future users of the tunnel are surely relieved, impressed, and happy that the tunnel has been opened at all.
Also, the original price tag was CZK 20 billion or so. The estimate grew to CZK 30 billion at some point and the final expenses are said to be CZK 43 billion. Because USD 1 = CZK 24 or so, it's still beneath $2 billion.
The tunnel is 5.5-6.5 kilometers long, depending how you count it, and is the longest city tunnel in Europe. It was open for traffic today, on Saturday September 19th, at 3 pm. The current female mayor of Prague (who is Slovak) and the Prague (Catholic) Archbishop Dominik Duka were the main VIPs at the opening ceremony. The current mayor (belonging to the Slovak oligarch Babiš's ANO movement) previously said that those who were building the tunnel were "idiots" but that didn't prevent her from presenting herself as the main hero and leader who has led the construction. ;-) However, the most important event that opened the tunnel was someone who clicked a mouse in the control room, we were told. ;-)
One side of the tunnel is at Malovanka, a place not too far from the Prague Castle, the tunnel continues in the Northeast direction, and the second opening of the tunnel is even more interesting for me. It's near the new Trója Bridge, just 200 meters or so from the Trója student hostels where I spent my five undergraduate years.
When I posted a music video of the Moldau by Smetana (1st part, 2nd part), I only used one photograph that seemed like fiction, at 7:36 of the second part. It looked like some bridges in the 22nd century. Science-fiction of a sort. I got that picture while searching for "Vltava" and it looked interesting even though I didn't know what it was supposed to be.
Alternatively, the picture was an exaggerated sketch of the new Trója Bridge that was opened about one year ago, in the early 21st century. I think that the bridge is a beautiful piece of modern architecture. The students who live in the hostels today may look at this thing all the time. ;-) See the hostels appearing at the end of this "drive through" video (left side) or the end of this sped up one (includes the bridge) or the beginning of this one.
So the second opening of the new Blanka Tunnel is right beneath the new Trója Bridge.
The speed is limited to 50 kilometers per hour. One needs a bit over 10 minutes to get from one side to the other. It seems to me that no one respects the speed limit because it takes 7-8 minutes to most YouTube drivers – or one minute if you speed up the video 8 times. ;-) (Update: Because of the totally smooth first two days, the maximum speed was raised from 50 to 70 kph on Monday 11 am.) It's probably significantly faster than the time an average driver spends above the ground these days. It's not unusual to spend way over half an hour while trying to go from one place in Prague to another by car.
The most comprehensive drive-through video I found is this 27-minute recording with all entrances and exits etc.
The price tag CZK 43 billion doesn't intuitively seem insanely huge. I have no idea whether the contract was overpriced but I guess that the answer is No.
But this amount is still 10 times larger than the announced costs of the modernization of the Pilsen-Rokycany railroad (the initial part of the tracks going from Pilsen to Prague), 15 km, which includes a pair of the longest railroad tunnels in Czechia, 4,200 meters (times two), complete modernization and doubling of the capacity of about 7 bridges, new light modern railway stations, and other things. The total cost of this contract is just CZK 4 billion, about $150 million.
It's absolutely beyond my thinking how someone can build something like that for CZK 4 billion only. Tens of millions of cubic meters of rock must be moved by kilometers, just in the railroad tunnels, and lots of other things. From some point of view, the Blanka Tunnel in Prague seems to be a comparable project to the Ejpovice Tunnel – so why is the Ejpovice Tunnel 10 times cheaper?
If someone has some good intuition about the price of similar projects or what the price has been in your country etc., I am sort of curious.
Update: I've lived in Boston for 6 years and when I think about it, the Big Dig is truly analogous to Blanka in character and length. The Big Dig's final price tag was over $14 billion, more than 8 times higher than in Prague. But some above-the-ground roads are included in that amount as well so it's hard to compare the numbers directly.
But yes, I do feel that even the same thing would end up being cheaper in Prague. Things' being cheaper in the Visegrad countries is an important reason why the GDP (parity purchasing power) per capita in Warsaw, Prague, and Budapest has already exceeded that of Vienna's.