The Roman Arena (in Romanian Arenele Romane) is the best event venue Bucharest has to offer. It was built over 100 years ago by King Carol; this helps understand the architecture that includes a royal lounge sitting across from the stage. The shape is that of a Roman amphitheater with a monumental stage guarded by imposing columns and decorated beautifully.
Over the years, offices and recording studios were added, the venue is now a hub for music and arts. Most of the studios are rented out to local bands and there’s a music school in the various rooms around the place.
When events take place, the location in a park helps a lot with the preparations; when I go there with my friends, we always go early and hang out in the park before the show. Also, in the morning, the walk back home is very pleasant and if you catch the sunrise, it’s incredible. It’s not rare to get back home at 10 in the morning after a succesful event “at the arena” (in Romanian it’s “la arene”).
The venue is not opened around the clock, you’ll need to research the schedule to find something suited for your taste, but that’s easy as there are a couple each week. I had some legendary nights at drum and bass parties in this venue, but also house/techno, rock concerts and everything else; my best one yet was a Faithless concert almost 10 years ago.