Eh'häusl ("Little Wedding House") is the "world's smallest hotel," located in Amberg, north of Munich. It dates to an 18th century ordinance that required couples to own a house before they got married, so some clever fellow slapped a roof and walls up to enclose a narrow alleyway between two other buildings. It wasn't intended to be livable, but rather to satisfy the formal requirement of "home ownership" for a marriage license. The house was passed from non-owning couple to non-owning couple for generations, and thus marriages continued in Amberg.
There is no reliable record of how long the practice continued, but the building survived, and in 2008 it received a complete refurbishment, transforming it into a luxury hotel. Total size? 56 square meters. Maximum number of guests at any one time? Two. [Google street view]
But there's more! According to an old legend told by the locals, couples who spend their wedding night at the tiny hotel are guaranteed
*to live happily ever after and never get divorced!