With more countries getting nuclear weapons, and madmen taking power and threatening to use them, we should all know what to do if a bomb falls on our city.
There are three likely possible causes of death from the blast.
1. The initial burst of radiation.
2. The heat generated by the bomb.
3. Physical damage to the area, which causes building to collapse.
The best way to survive is to be far away, but if you are not, you can fill a metal bath with water and sit in it.
The bath, being metal will absorb some of the radiation and reduce the dose you are exposed to.
Water has a high heat capacity, and will absorb a lot of energy in heating up. This will reduce the increase in temperature.
The bath itself will provide a very basic cage to reduce the danger from a collapsing building.