Circular prisons achieve greater security at lower cost than conventional designs

Evidence

The circular form, notwithstanding its taking demonstrably less materials than any other, may, for aught I know, on its first construction, be more expensive than one of equal dimensions in any of the ordinary forms. But this objection, which has no other source than the loose and random surmise of one who has had no experience in building, can never have held good in comparison with all the other prisons that we have, if in truth it holds good in comparison with any. Witness the massy piles of Newgate, of which the enormous, and upon the common plans by no means unnecessary expense, has been laid out in the purchase of a degree of security, not equal to that which the circular form would have given to the slightest building that could be made to hold together. — Jeremy Bentham, The Panopticon Writings, 277