Radetzky Wave breaks under the Radetzkybrücke bridge on the Mur River in Graz, Austria, and it's been surfed since 1999 — making it the oldest river wave in the country and a true OG of European river surfing. Entry is on a rope, and it gets tricky at both ends of the flow range: low water chews up fins, while high water brings real risk of getting worked, so this is advanced-rider territory. Watch for rocks sitting close to the surface near both banks, and know the wave before committing if you're new to it. If you're just starting out in Graz, locals will point you to the gentler Hauptbrücke wave and save Radetzky for when your skills match its reputation.