Myfi
I did a little research - check out:
http://www.encspb.ru/en/index.php?pg=0&dir=&level=2&kod=2803920674Unfortunately the cemetery I suggested (Novodevichie kladbishe) behind Mother of God Kazan did not open until 1845. The next nearest - Gromovsoe kladbishe opened in 1835 but is now derelict (information available only in Russian on the same web-site). The oldest and largest cemetery is however Volkovskie kladbishe - 26 Hectares, opened 1719. It is not so far away. I will check this out in the spring as I also have relatives there. Unfortunately, there are over 13 km of footpaths - a needle in a haystack.
Regarding sixverst, I had some inspiration. I think I told you a Verst was 1.067 km and that distance is commonly used to mark featureless terrain? Well, I noted than some railway stations are simply 5km, 7km, etc. There is one station 6km in the north next to the Ford factory - it was previously a brick factory. In the south, there is a 5km station and a 7km station. The station halfway between is the Lomonosov Porcelain factory stop. Any chance your ancestors were involved in either brick or china works?
Malcolm
St Petersburg