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!