My own personal headcanon, back from when I was a 90s kid Trekker, was that "Leningrad" is the name of a popular (presumably Soviet-styled) theme park.In the Star Trek Universe, the Soviet Union never fell or got back again in the 23th Century.
I mean, hey, it's been 300 years...it'd be like a Ren Faire, or Disneyland. People from the actual 1600s would probably find those baffling, too.
Just be glad we didn't get to see the park they have in Germany. Eek.