Ottarshögen is an large burial mound built in the 6th or 7th century AD. According the folk legend, it is a grave of ancient Ottar Vendelkråka, the king of Svealand in the early 6th century. Archaeologists have anyway dated it to the Vendel Period. The mound is 37m wide and 6m high.
References:The city walls of Avila were built in the 11th century to protect the citizens from the Moors. They have been well maintained throughout the centuries and are now a major tourist attraction as well as a UNESCO World Heritage Site. Visitors can walk around about half of the length of the walls.
The layout of the city is an even quadrilateral with a perimeter of 2,516 m. Its walls, which consist in part of stones already used in earlier constructions, have an average thickness of 3 m. Access to the city is afforded by nine gates of different periods; twin 20 m high towers, linked by a semi-circular arch, flank the oldest ones, Puerta de San Vicente and Puerta del Alcázar.