St. Petersburg is an interesting place, and has become my most favorite city in the world to visit (supplanting Barcelona). Beyond all the historical stuff, there is a great vibe about the city and the architecture plus history cannot be beat. That said, they have a very interesting waterway navigation situation. St. Petersburg is constructed on a marsh and the founder decided he wanted to have a large island in the middle as in integrated part of the city. The consequence, of course, that this island had to be connected by bridges to the rest of the city. Alas, when they put bridges in, they were all very low and are draw bridges. For most of the year, these work on a time table. They are down (and impassible by most boats) from 4AM until 1AM allowing the city people to make it back and forth unencumbered. At 1AM, however, these bridges go up all around the city at the same time!! The result is, if your hotel is in that part of the city and you are on the wrong side, too bad. Between the up hours, 1am-4am, boats race in and out. It is quite a site to behold.
Vladivostock is a true working ocean going port, along with Russia's Pacific Fleet head quarters. It isn't a pleasure yachts type place. It is rough, the edges are hard, and no nonsense. I'd sit in my hotel room and watch Navy, cargo, fishing, and tugs work the harbor 24x7. I could imagine the faces of the working boat man look at us like a bunch of lunatics navigating our sailboat through their office environment. I doubt they have much in the way of facilities for boats like ours and that the immigration process wouldn't be tailored to a family of 4 just trying to visit the city or seeking repairs of some sort. All is well, however, as the city itself offers very little interest to world explorers.
Incheon Korea is an interesting harbor. It was wide, well marked, and full of all kinds of boats. It was clean and felt very comfortable. I'd see big ships and little boats all respectfully passing through. Of course, this was from my hotel room and there may have been lots of chatter going on. Incheon provides an excellent gateway for visiting Seoul, and it is very possible that we will find our way there during the voyage.