After a couple of nights in Ruse, I crossed the Danube into Romania. On the Bulgarian side, there’s only toll, which wasn’t applicable to me. On the Romanian side there were 5 or 6 lanes of cars moving very slowly. No indication that it was passport control. I changed lanes at some point, which is apparently not allowed.
A few minutes later an official waved me over into one of the closed lanes and then went back into his booth. When I arrived at the booth, I stood around for maybe a minute or two. When he didn’t pay me any attention, I figured this is just for cars and slowly cycled on.
A dozen seconds later he started yelling that I must come back. It turns out it was passport control. Fortunately he was very friendly.
Note that some maps will show “Pyce” when Ruse should be. It is not a mistake. It is just Ruse written in the Bulgarian alphabet.