Starting at Innere Stadt, 8010 Graz, Austria, open the Explorial app and enter the 6-digit game code that you received by text and Viator chat message. Graz's old city is compact enough to cover on foot and deep enough to reward every step. The first riddle leads you to the Rathaus, Graz's imposing neo-Renaissance town hall on the Hauptplatz, whose clock tower and colonnaded courtyard have anchored civic life here for over a century. From there the app guides you to the Kunsthaus Graz — the 'friendly alien' as locals call it — a bulbous, blue-grey contemporary art museum designed by Peter Cook that landed in the old city in 2003 and has been starting conversations ever since. Next you find the Glockenspielplatz, a small square where mechanical figures emerge from the clock tower to perform a traditional dance at set hours — a piece of mechanical theatre that has delighted and puzzled visitors for decades. Allow around 2 hours for the route. Comfortable shoes are ideal for Graz's cobbled lanes.