The ancient fortress on an island in Siberia

Deep within the Siberia there is a lake which is just one among thousands of others. In the center of that lake there is a small island. On that island people excavated the remains of an ancient fortress, which dates from 1500. A lot more excavations need to be done so that the Fortress can become a tourist attraction, but still, from the air, it's beautiful at any time of the year. The first set of pictures was taken during the short Siberian summer:

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