Perched in a commanding position over the Waal River, the Valkhof is a lovely park and the site of a ruined palace begun by Charlemagne in the 8th century and continued by Emperor Frederick Barbarossa from 1155 (see it in better days in the Jan van Goyen painting at the museum across the way). All of it bar two side chapels was destroyed in 1796: admire the 16-sided Sint Nicolaaskapel, a rare example of Byzantine architecture in the Netherlands, and the ruined Sint Maartenskapel.