How many letters does the top answer for “capital of russian empire” have?

The most common answer is saintpetersburg (15 letters).

Crossword clue: capital of russian empire

1 answer found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

saintpetersburg 15 letters wd-fact-v3

city in russian empire 50% similar → aneniinoi, kelme, kokshetau

desert in russian empire 50% similar → ryndesert

dish from russian empire 50% similar → oliviersalad

lake in russian empire 50% similar → charvaklake

mountain in russian empire 50% similar → mountadelung, sherkala, shkhara