Idea for a TV series
It looks like a perfectly ordinary apartment building lobby, with only one visible oddity: all the doors leading off it are different. This is because each door leads to a different moment in time. Through this lobby you can walk through history, from age to age, but each door leads to a knot in the skein of history, a problem that might rewrite the past and which must be solved to set time back on the right track. Solve it and you will find the door that will lead back to the lobby, where all the doors will have changed again, leading to new moments in time, once of which, one day, might be your own.