Exposed by meanderings of the Río Chubut after an earlier subtropical sea evaporated, Bryn Gwyn’s sedimentary badlands are an open book of Tertiary fossils. The oldest beds are too recent for dinosaur bones, but there is evidence of marine mammals such as seals, dolphins, and whales along with penguins, giant anteaters, and ungulates from times when this was savanna.
Visitors to the park, eight kilometers south of Gaiman  via RP 5, can hike the well-organized trail, which climbs gradually and then steeply up the cliffs from the south-side confitería. There are at least a dozen excavations, with some fossils in the open and others preserved in glass cases.
Affiliated with Trelew’s Museo Feruglio , Bryn Gwyn charges US$2.50 admission for adults, US$1 for children; groups larger than 20 can arrange guided visits. Hours are 9 a.m.–6 p.m. Tuesday–Sunday. There’s no scheduled transportation, but remises from Gaiman are not unreasonable.