Although I've been living around Dupont Circle for about a year by now, I learned about Dupont Underground just recently and absolutely accidentally.
Built around 70 years ago, it's a set of underground tunnels and passages below Dupont Traffic Circle in Washington, DC. At that time there were streetcars (that's "trams" outside of US) in the District and since Dupont Circle was already quite busy with cars, somebody come up with an idea to put streetcars underground so they don't get in a way of regular vehicles. That's how Dupont Underground, although not yet called like that, was built and was in use since then until Capital Transit was shut down in 1962.
Once streetcars stopped running, rails were removed and the tunnel entrances were filled with concrete and paved away. The only remnant that was left in place - closed pedestrian entrances around traffic circle. In 90’s someone attempted converting tunnels into a food court but abandoned the idea in few months. It was unused for more than half of a century and was acquired by a non-profit just recently with a goal to convert it into an art space. They giving tours around the underground complex on weekdays and that's how we've gotten inside.
Only a tiny part of the space is "civilized" to some degree by now - meaning that there is light and it's clean - and that's the so-called "east platform". Most of the tunnels are still in their "original" state and are waiting to be taken care of.
The part that was already cleaned up is actively used by the community - there are fresh graffities on the walls and regular exhibits and events taking place every now and then. For instance, just a few weeks ago there was an exhibition called "Re-Ball" and it made use of more than half of a million of ball-pit balls that once were residing in National Building Museum.
Once you reach the end of the east platform you have to turn on your portable light - from now on you're going to be moving in complete darkness.
With the only exception of west platform section, that is filled with debris from the abandoned food court, most of the tunnels are either empty or filled with some art installations - some of them are designed specifically for Dupont Underground and some just don't have any other home (as it usually happens with some of installations from Georgetown Glow once it over).
The only way to visit Dupont Underground and see all of the tunnels is to get a ticket for a guided tour. They're are not very expensive but conducted only in groups. Although that makes perfect sense I wouldn't have minded to pay more to get a personal tour or at least a tour with a smaller group. Just because with a huge crowd it's harder to enjoy atmosphere of the place.
Our guide was just amazing and she told us all the history behind the place and answered all sorts of crazy questions we had.
Except the only one.
Why there is a dentist chair inside the abandoned women restroom?..
After wandering through the dark tunnels for a while, you inevitably being affected by a feeling of something mysterious and thrilling. Some random art appearing out of the darkness under the light of your flashlight perfectly finishes the atmosphere.
The official tour, at least nowadays, ends at the conjunction of north tunnels - just at the place where in the past there was a railway going outside, back to the aboveground. From there - you're free to wander through the north-east tunnel back to the east platform where you can exit the complex. But before that - there is a piano within the large underground space with an amazing acoustics. Luckily, we had a guy in our group who knew how to play a piano so we were able to enjoy the moment. I think that's just an amazing attraction and I hope it will see more development in the future. It's hard to express how it feels being down there below the ground listening to the piano in almost complete darkness but at least there is only a short video I captured on my phone in terrible quality as I forgot to bring my camera with me.