It means that Milan is lucky because it has some among the best masterpieces of the Reinassance art. "Ad ogni modo" means "anyway" and is probably related to a previuos sentence. "Si è ritrovata in casa" means literally "it has found in its home"; this means that Milan has the Reinassance masterpieces "for free/without doing efforts". I hope to have helped you! If you did not understand you can ask me!