Sorry to burst your bubble, but that's far from the heaviest, too. Your completely hollow safe has nothing on this 3650lb lead-acid battery pack for a UPS system. http://www.amazon.com/gp/aw/d/B005LXOOIU/ref=mp_s_a_1_1?qid=1389082386&sr=1-1

They used to Prime ship a 9000lb UPS, too, but it looks like that's off Prime these days. http://www.amazon.com/gp/aw/d/B005LXOOIU/ref=mp_s_a_1_1?qid=1389082760&sr=1-1

/ I work for an AMZN subsidiary, and we've totally played this game in our office. A bunch of the others kept finding heavier and heavier generators and safes, until I pulled out the UPS card, since they are basically required to be like 90% lead.