I'll weigh in here. I am a practicing member of the LDS church (Mormon) and I have been through the temple more times than I can count. Mormons use temples to be closer to God and to make sacred covenants (promises) to Him. These promises do not vary from anything that Christ teaches in the Bible. We believe that the temples are the house of the Lord and are very sacred places. There is a difference between secret and sacred. There is a lot of biblical symbolism in them. If you search LDS temples, you can see pictures of the inside of them. Also, when a new temple is built, before it is dedicated, they hold an open house where anyone can go through and see everything. I highly suggest trying to go to one if you can as they truly are incredibly beautiful buildings. As far as security, anyone can go into the main lobby, where you will likely find an elderly person at the front desk with a smile on their face. I've never seen "security" at any of the ones I've been to.