Unfortunately, I only found Tandoor at the end of my stay in St. Petersburg. Even though the restaurant is not 100% vegetarian, the vegetarian selection is excellent. I had the Vegetarian Chef's Special, a feast of about ten different dishes for RUB900, a bagatelle for the quantity of food, not to mention the excellent quality. I thought it was worth every single Ruble as each dish was more delicious than the other. The food was not too spicy and perfect for those who don't appreciate extremely spicy dishes. The staff spoke English perfectly and everyone was extremely polite. Another plus is that this is a non smoking restaurant, something hard to find in Russia. It is located within walking distance of the Hermitage and it makes the perfect spot to eat after a long day at the museum. No doubt this will be my first stop whenever I go back to St. Petersburg.
The only reason I'm not rating them 5 happy cows is because the restaurant is not 100% vegetarian.
Cons: Not 100% vegetarian