Be aware that this is actually a little known monument, and many people you ask will instead direct you to the Blockade Museum. There is a monument at street level, but the museum itself is underground. There are 12 small display cases, each portraying a different aspect of the Siege (rations, cultural events, military, etc.), and a display with 3 very large copper tablets which are changed daily, each one telling the story of what happened on that date during the Siege. Very reverential atmosphere. The day I visited, there was a chorale performance and poetic recital by childhood survivors of the Siege (or their relatives), many of whom were wearing the "Hero of the Soviet Union" medals they had been awarded. Be sure to combine this visit with visits to the Blockade Museum and Piskaryovskoye Memorial Cemetery.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.