Fossil Park, Sylvania

Sylvania is built on shale, and that is the whole reason this park exists. The city sits on large shale deposits that have been quarried for generations to make concrete, cement and other stone products, and the silica shale from this region is renowned among palaeontologists for the quality of its early Devonian fossils.

Fossil Park opened in 2001 and works on a simple principle: rather than let visitors loose on a working quarry, the quarry comes to them. Loose shale is brought in and piled up, and you break it apart looking for what is inside. Trilobites are the prize. The shale splits readily, so the barrier to entry is close to zero, which makes this one of the easiest places in the Midwest to put a genuine Devonian fossil into a child's hand within about ten minutes of arriving.

The park is run by the Olander Park System, which also programmes guided fossil collecting sessions through the season for anyone who would rather be shown what to look for than work it out from scratch. If you have never split a rock before, that is the version to book.

Turning up costs nothing. Parking, admission and the digging are all free, you keep whatever you split out, and the one rule that catches people out is that tools are banned: no hammers, no picks, no shovels. The shale comes apart in your hands. The pit runs mid April to the end of October, opening at half past eight and closing somewhere between half past five and half past seven depending on the month, and it is shut for the winter.

What is in the shale is early Devonian and marine. Ohio then lay under a warm shallow sea, and what lived and died in it settled into the mud that hardened into this rock. Trilobites are the fossil the park is known for.

Sylvania itself is a city of around 19,000 on the western edge of Toledo, with a creek running through it that becomes the Ottawa River and empties into the Maumee. The park sits alongside the rest of the Olander system, which is to say you can turn a fossil hunt into an ordinary afternoon out without driving anywhere else.