In Pioneer Square (Seattle) we took the Bill Speidel UndergroundTour. It had lots of old artifacts and the narrator described an important piece of Seattle's history. Much of the town was built too low relative to the water table and there was lots of flooding from the river, rotten wood, etc. A massive rebuilding project was instituted to raise the level, and to use stone foundations instead of wooden ones. The tour was very interesting and well worth it.
I suppose in the future as the sea level rises there will be potential for many more instances of tours like this - especially in the Miami Beach area.