I Was Once Told When Visiting Amsterdam,

the canals have three layers,

starting at the bottom, one meter of mud, on top of that one meter of bicycles, and finally one meter of water for the boats, I am not sure if that is true, but when excavations between the Central and Rokin metro stations along a former piece of the Amstel river in Amsterdam started, approximately 700,000 objects found from 119,000 BC to 2005, when the construction works started, 

You can see all of it online, organized by date or sorting them by material, the location where they were found and their use, there is also an offline collection, displays of arranged objects next to the escalators of the brand-new Rokin metro station in the heart of Amsterdam. What’s special about the archaeological documentation, is that all artefacts are treated equally, no matter how old or profound they are. Every piece is seen as valuable part of Amsterdam’s history, scrolling down on the Below The Surface website I am amazed at how well many of the objects have been preserved, but no bicycles as far as I could see!