The Washington Mews is probably the most beautiful street in NYC. I would compare it to Rue Cremieux in Paris or Portobello Road in London. You won't find it so easily though. It is a small gated street right near Washington Square Park but you can easily miss it. The gate is always open however it is technically a private street. Most of it is owned by NYU. I never had a problem walking through it, and nobody will bother you.