P1: Rosberg heads Hamilton
Nico Rosberg set the early pace ahead of Mercedes team-mate Lewis Hamilton in opening practice for the Austrian GP on Friday.
Rosberg, the current World Championship leader, lapped the 4.326km Red Bull Ring in a time of 1:11.295s to go 0.140s faster than Hamilton, with Ferrari's Fernando Alonso third fastest from Williams driver Felipe Massa.
As might be expected, given that just four drivers have F1 experience at the track - which last hosted a grand prix in 2003 - there was plenty of activity during the 90-minute session, although light rain forced all the cars back to the pits at one point.
A combination of the learning process and green track conditions also caught a number of drivers out; the Red Bull Ring might only have nine corners but several proved challenging, with the last proving the most difficult of all.
Playing a starring role in that respect was World Champion Sebastian Vettel, who got out of shape and was lucky to avoid damage when his car performed a lurid 720-degree pirouette exiting Turn 9.
Vettel ended the session 15th fastest overall and with team-mate and Canadian GP winner Daniel Ricciardo 13th, it was a slow start to the weekend for Red Bull at their home race.
Rosberg and Hamilton aside, Mercedes-powered cars accounted for eight of the top ten runners, with Alonso as usual the exception to the rule and Toro Rosso's Jean-Eric Vergne the best-placed Renault runner in tenth.
McLaren's Jenson Button was fifth fastest ahead of Force India pair Sergio Perez and Nico Hulkenberg, with Valtteri Bottas (Williams) and Kevin Magnussen (McLaren) completing the top ten positions.
Kimi Raikkonen's Ferrari was 11th fastest as both the Scuderia and Mercedes trialled titanium skid blocks on their cars - the resulting sparks intended to create a more spectacular look out on track.
Even so, the effect appeared muted at best and - much as was the case with the exhaust trumpet trialled in Barcelona a couple of months ago - it remains to be seen whether the experiment will continue.
Despite ending P1 on top, Rosberg's session was not without its problems, with his W05 spending time in the pits early on after an ERS cooling pump failed.
Car problems for Bottas, Adrian Sutil and Marcus Ericsson - respectively 21st and 22nd fastest - brought an early end to their morning's work, with an electrical failure on the Swede's Caterham giving them a race against time to remedy it for P2.
Second practice starts at 1pm BST.
This weekend's Austrian GP is live only on Sky Sports F1. Race Day coverage begins with the Track Parade at 11.30am on Sunday