It appears you are referring to a recent news headline. However, Alexei Navalny, a notable critic of Vladimir Putin, is not dead. As of my last update, he is in prison. The grave you might be referring to could be of Boris Nemtsov, another prominent critic of Putin who was shot dead in 2015. His grave has become a place of pilgrimage for opposition supporters. Please provide more precise details if you are referring to a different event.