Back in 2008 I commented on the awesome floor numbering system in an Israeli elevator, where ground level was the 0th floor, and underground floors got negative numbers. Well, when visiting a doctor to follow up from my gallbladder adventures, I saw this elevator:
This is the first time I've seen this numbering system in the US. While it's not as cool as the 0th floor in that they use L (presumably for "Lobby" even though there wasn't one), their underground floors got negative signs!