Among the six kinds of forts described in the scriptures, among every kind of other forts the service and the love of the subjects is of the most impregnable.
दुर्गेषु च महाराज षट्स ये शास्त्रनिश्चिताः। सर्वदुर्गेषु मन्यन्ते नरदुर्गं सुदुस्तरम्॥