Amsterdam is building a new subway line directly beneath the Amstel River, so they drained it, as one does. Then they let a team of archaeologists go wild:
The excavations in the Amstel yielded a deluge of finds, some 700,000 in all: a vast array of objects, some broken, some whole, all jumbled together. Damrak and Rokin proved to be extremely rich sites on account of the waste that had been dumped in the river for centuries and the objects accidentally lost in the water. The enormous quantity, great variety and everyday nature of these material remains make them rare sources of urban history. The richly assorted collection covers a vast stretch of time, from long before the emergence of the city right up to the present day. The objects paint a multi-facetted picture of daily life in the city of Amsterdam.
The city has published an online catalog that you can view chronologically or alphabetically.