The second door is usually another thick steel door and it is at the beginning of a shared hallway. This door does not have an intercom, just a huge lock and key. The next door, the actual door to the apartment, is also a thick steel door with a big key and a peephole. Last, but not least, there is an interior door, just inside the main door, that is used to keep out dust and drafts from the hallway. Each of these doors has a key, but not everyone always has keys to all the doors.
Keys are hard to come by here.
I personally know of only two places in Moscow where keys can be made, and not even the most connected Russian can produce an extra domaphone key. I have seen grown women break down in tears where they loose a key, or worse, an entire keyring. When you receive a key here, that is the day you are considered a true friend or part of the family. Wednesday night a friend of ours spent the night. The next morning she got up after all of us, so instead of waiting for her to leave, I gave her the keys with instructions of how to get out of the house and drop the keys off at my work.