The Dole is the largest island in the Daugava River, surrounded to the Northeast by the rapid waters of the Daugava and to the Southwest by calm and gradually overgrown waters from Dry Daugava.  The island is a specially protected nature park, established in 1986 to protect the landscape and cultural and historical values of the island in the wake of the construction of the Rīga hydroelectric power plant, as well as rare and protected species of plants and animals.  The island is also meant to provide education and leisure for visitors.  Best known on the island is the Daugava Museum, which is in the mansion of the old Dole Estate.  The museum features some 13,000 exhibits that speak to the history of the island and the river – Baltic and Livonian apparel, tools and household objects.  The exhibition also presents the Daugava as an important waterway and the related history of forms of transport and rafters.  In the park is an open-air exhibition with reconstructed lamprey eel traps and a barrier to fish salmon, along with a set of fishing tools.  A dolomite cliff is alongside the museum on the steep shore of the Dry Daugava.  The ruins of the Vecdole castle can be found on the south-eastern end of the island, near Bēči.