The Floating Market is the place to buy and sell things in London Below, the place described in Neil Gaiman's Neverwhere. Every time, it is held in a different place; and there is a market truce that guarantees that there is no fighting within the Floating Market. This is heavily enforced and greatly useful, since London Below is so incredibly dangerous. It can even be held in places in London Above (e.g. Harrod's), but somehow people from London Above don't notice it.