Standalone short: the viking-age runestone built into the gate of Sweden's newest fortress — the oldest stone on the youngest castle. Leif + Margareta.
Built into the gate of one of Sweden's newest fortresses [pause] was its single oldest stone. To find it, you have to look up — above the door of the tower.
It was a runestone — carved in the age of the vikings, centuries before the fortress existed — set straight into the wall above the tower gate. It survives still, drawn by Anders Hedenberg and now kept in the Gothenburg museum.
And the island's own name gives the game away: Kyrkogårdsholmen — Graveyard Island. People had used this rock long, long before any fortress stood on it. There was deep time here, buried under the new stone.
So when you stand at that gate, you are standing at both ends of the story at once: the newest fortress in the kingdom, and a stone from the world that first fought over this river, a thousand years before. Älvsborg, reaching all the way back.