The depression has high walls with layers of exposed rock that should reveal significant new information about the Red Planet's geological past.
Opportunity has been exploring Mars' Meridiani Plains since January 2004.
Its "twin", the Spirit rover, continues to explore Gusev Crater on the other side of the Red Planet.
Both robots have continued working far beyond their designed mission lifetimes.
Opportunity has now driven more than 9.2km (5.7 miles) across the planet's dusty surface, examining rocks and studying the Martian environment.
Water story
It has found strong evidence that its region of Mars was covered with shallow waters many millions of years ago. The investigation of rocks at Victoria is expected to fill out the story still further.
"This is a geologist's dream come true," said Professor Steve Squyres of Cornell University, the principal investigator on Nasa's rover programme.
"Those layers of rock, if we can get to them, will tell us new stories about the environmental conditions long ago.
"We especially want to learn whether the wet era that we found recorded in the rocks closer to the landing site extended farther back in time. The way to find that out is to go deeper, and Victoria may let us do that."
The Spirit rover has been holed up at one northward-tilted position through the southern Mars winter in order to collect the maximum energy supply for its solar panels.
Spirit is conducting studies that benefit from staying in one place, such as monitoring effects of wind on dust. It will begin driving again when the Martian spring increases the amount of solar power available.
Both rovers will be on a reduced workload through October as Mars passes behind the Sun as viewed from Earth. This makes communication with the robots more difficult than usual.
^ Back to top | BBC Sport Home | BBC Homepage | Contact us | Help | ©
~RS~q~RS~~RS~z~RS~41~RS~)