Church Project Theorem: Upper v. Lower Church
The Project's most dreaded conundrum, and the single biggest detriment to church visits, Upper v. Lower Church refers to a construction tactic common to older churches. Many of these buildings have both a small basement (lower) church, and a larger, more ornate upper church. The lower church was almost always the first part of the church built, giving the parish a place to have mass while they constructed a much more suitable home above.
These lower churches were never intended to be a parish's main worship space, but given the insane costs of heating and maintaining large upper churches, many struggling parishes hold most (if not all) masses downstairs to save money, especially in the winter.
Interesting note: In some parishes, the plans for a larger upper church never came to fruition, so they got stuck with flat, generally unappealing lower church-only buildings. See Olney's St. Ambrose, or Feltonville's St. Henry.