Meeting at the parking lot P3 Bahnhof immediately behind the WI Mainz-Kastel Bahnhof. (NOT downtown Mainz!)
From Frankfurt:
Take A66 to B455 in Wiesbaden.
Take exit 6-Wiesbaden-Erbenheim to merge onto B455 toward Mainz-Kastel / Wiesbaden-Erbenheim-Süd
Follow B455 to Rheinufer
Go through 1 roundabout
At the roundabout, take the 3rd exit onto Philippsring / B40
Turn next right onto Rheinufer
GPS: 50°0′25″N 8°16′57″E