WALTHAM, Mass. — After bringing in Kevin Garnett and Ray Allen in the summer of 2007, the Boston Celtics went to Rome for training camp so the new players could get to know each other.

They returned from the overseas bonding experience and won the NBA championship.

Now, as the team heads back to Europe, the Celtics are hoping to do it again.

“Whenever you go on a road trip — even during the season — it’s never a bad thing,” said Coach Doc Rivers, who has long felt that the Roman holiday helped the new Big Three of Paul Pierce, Kevin Garnett and Ray Allen become better acquainted and jump-start their run to the 2008 NBA title. “The craziest thing is their cellphones don’t work over there. So they have to talk to each other on the buses.”

The Celtics practiced at their workout facility on Wednesday before they were scheduled to leave for Istanbul and Milan, where they’ll resume training camp and play a pair of exhibition games.

More importantly, the team believes, they’ll spend countless hours together on planes, in restaurants and just wandering unfamiliar streets.

“It’s about being a unit,” said guard Jason Terry, one of a handful of new players on the roster. “One thing is to get with my teammates, out of our comfort zone where we depend on each other.”

Rivers said his only regret about the trip is that he has to interrupt camp for the flight to Turkey, then give the players a day off after just three days of practice. They will play Fenerbahce Ulker in Istanbul on Friday, then travel to Milan and play Emporio Armani on Oct. 7; they return to Boston on Oct. 8 and get another day off before resuming practice on Oct. 11 and playing their first U.S. exhibition game against the New York Knicks in Hartford, Conn., two days later.

By that time, Garnett said, they should have a better idea of what to expect this season.

“From a basketball standpoint,” he said, “we’re still getting to know each other.”

Rivers said he didn’t know much about Turkey but he would know plenty after spending 11 hours on the plane on the way over.

He’ll also learn a lot about the nine players on the 16-man training camp roster who are new to the team.

A handful of them are expected to make the final roster, including Terry, who joined the team as the likely replacement for Allen at shooting guard.

Draft picks Jared Sullinger, Fab Melo and Kris Joseph will also get their introduction to life in the NBA.

“It will give them a little taste of what a long road trip is like,” Rivers said.

The Celtics begin the regular season on Oct. 30 against the defending champion Heat at Miami.

Boston plays its first regular-season home game on Nov. 2 against the Milwaukee Bucks.