Starting at S:t Eriks torg, between the cathedral and the river, you'll open the Explorial app, enter the 6-digit game code that you received by text and Viator chat message, and set off through the university quarter. The tour is fully self-guided — no guide, no fixed start time, just your group and the city. Uppsala Castle looms pink on its hill — built by Gustav Vasa, scene of abdications and intrigues. Riddles storm the ramparts painlessly. The University Main Building follows, its 19th-century aula echoing with four centuries of scholarship. Trivia tests whether you'd have passed the entrance exam. Then a sweeter challenge: Güntherska Hovkonditori, the classic patisserie where clues come with a strong hint to stop for fika. Around two hours covers castle hill to café. The leaderboard graduates the winner with honours.