Where in St Petersburg have you seen metal doors? Banks, prisons? I live in St Pete, so stop telling lies - if your granny likes playing soldiers, fine, but please don't speak about the rest of the city. Metal doors with code locks? Where on earth are those? Secret weapon factories? A word of advice in your ear - knock off the booze, it's beginning to really show.
Knock off the smart a** image VM, it's getting really annoying.

A lot of apartments have double doors, one of them made of metal. Often it is covered in wood paneling from the outside, so it doesn't look like metal.

The code locks are on the doors leading into the building itself from the outside. They are very common in apartment buildings away from the very center of the city. The lock is usually a 3 digit code or sometimes it is an intercom and you can call the person you're there to visit and they will unlock the door for you.

astarz, прости меня малыш, ду-ду-ду-ду-ру!
Gluk'oza!