Saint Petersburg is at the eastern end of the Gulf of Finland, where the broad River Neva enters the Baltic. About 60 km (40 miles) upriver lies Lake Ladoga, the largest lake in Europe.
There is no Old Town of narrow streets, squeezed within medieval walls. This city was started from scratch on empty marshes on 27 May 1703, by order of Czar Peter the Great. The Russian Empire was beginning to look westwards.
Arriving by sea, the first sight is Kronstadt naval base on Kotlin Island. You may catch a glimpse of its enormous Naval Cathedral. The waters are shallow from now on, and your ship will travel the rest of the way along the Main Sea Channel.
On the southern shore are the palaces where Russia's nobility once lived. Peterhof (Petrodvorets in Russian) is the grand palace of Peter the Great. It is sometimes visible from the sea because it stands on a ridge but it's too far away to see clearly.
Apart from Kronstadt and a few green suburbs, most of St. Petersburg is inland and is not visible from the sea. The historic centre is bounded by the River Neva on the North and West and by the smaller River Fontanka. The oldest part, the Fortress of Peter and Paul, lies just outside the centre, on the other side of the Neva.
Moscow is over 700 km (450 miles) away, and the road is not yet motorway-standard. Flying is the only viable way of adding Russia's capital to a Baltic cruise itinerary. The flight takes 80 minutes, and getting to and from the airports can add quite a lot more.