Hey! I have actually been to Saint Petersburg before and will go back this April with my Mum and am looking for a nice and quiet hotel, near the city center (which is in the 3-star-range from a Western European view). Thanks! :)
The nicest hotel in town is
W St. Petersburg hands down. Worth every penny.
The best budget stay (which is so much better than a hostel even for a Western European view) is
Soul Kitchen Hostel (Moika embankment 62/2 app 9 190000 St. Petersburg, Russia)
Hope this helps. Have a nice trip.
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The Astoria Hotel. Affordable, best location ever.