BARCELONA, Spain — A split second off the lead with the mighty Pyrenees looming, Lance Armstrong now gets to see what his rivals can throw at him.

After mostly flat, wind-swept stages along the Mediterranean rim this week, the Tour de France enters mountainous terrain that has long belonged to climbers.

Armstrong remained just a fraction behind overall leader Fabian Cancellara of Switzerland yesterday after a treacherous, rain-soaked ride filled with crashes. Thor Hushovd of Norway led a mass sprint finish to capture the 113-mile sixth stage from Gerona to Barcelona.

The field faces a 139-mile haul from Barcelona to Andorra today with a grueling uphill finish — the first and hardest of three days in the Pyrenees.

"Tomorrow is an important day," the 37-year-old Armstrong said. "I don't know if it's the most important day, but it's definitely a big appointment on this Tour."

The seven-time champion said he was happy to emerge unscathed from yesterday's "nervous" ride. Two spills marred the last six miles — one involving Yukiya Arashiro of Japan, another involving former world champion Tom Boonen of Belgium, one of Hushovd's sprinting rivals.

Cancellara, a time trial specialist, acknowledges he's not the best climber and his six-day run in the front may soon end.

"What do I have to do tomorrow? It's a good question," he said. "It's been a beautiful week to be in this yellow jersey. ... I'm going to try to defend it but I don't know how well I can do."

The mountains figure to play a bigger role in this Tour. Today's jaunt features the Serra Seca pass and a finish into Arcalis in Andorra that's so tough it's beyond classification in cycling's ranking system.

TOUR DE FRANCE AT A GLANCE

Stage 6: 112.8-mile trek, Gerona to Barcelona along the Mediterranean Sea featuring five small climbs.

Winner: Norway's Thor Hushovd of the Cervelo team, in 4 hours, 21 minutes, 33 seconds, in a mass sprint finish.

Yellow jersey: Fabian Cancellara of Switzerland, who maintained his lead of a fraction of a second over seven-time champion Lance Armstrong.

Next stage: Stage 7 is the first big mountain stage, taking the riders 139.2 miles from Barcelona to an uphill finish at the Arcalis ski station in Andorra.