The mysterious transparent bubble that envelops the small town of Chester’s Mill on CBS’ popular summer drama “Under the Dome” is said to be “invisible, indestructible and completely inescapable” by one of the show’s characters. Somehow, the nation’s biggest movie studios have been able to break through the barrier.

Each ad break in the first three episodes CBS has broadcast of “Dome” has included a commercial for a movie. Among the films advertised so far are “Pacific Rim,” from Warner Bros. and Legendary Pictures; “R.I.P.D.,” from Universal; “Grown Ups 2,” from Columbia Pictures; “The Lone Ranger,” from Disney; “RED2,” from Summit Entertainment”; “The Conjuring,” from Warner; “ 2 Guns,” from Universal; and “The Wolverine,” from 20th Century Fox.

Even some decidedly non-traditional content purveyors are scurrying under “Dome.” Netflix ran an ad in the series’ second episode to promote the comedy “Orange Is the New Black,” and CBS has run a promo each week to alert viewers to the fact that episodes of “Dome” are available on Amazon’s video streaming service.

TV has long been a showcase for movie trailers, but the case of “Dome” may be worth studying under glass. CBS wins its share of movie commercials, but the network typically fares better with ads from pharmaceutical concerns, auto marketers, retailers and telecommunications and technology advertisers, said Jo Ann Ross, president of ad sales for CBS. And movie studios typically place more emphasis on Thursdays, where their ads can influence TV viewers to attend an opening weekend. CBS airs “Dome” on Mondays.

“’Under The Dome’ is a great story – with the studios coming in over the summer to to original programming on a Monday night and spending the money to support it,” said Ross. We also have movies going into the repeats on Sundays. There are several studios there with multiple units.”

Warner Bros. has been a strong supporter of the show. In the debut episode, Warner ran a 90-second extended preview of “Pacific Rim” during the first commercial break. Since that time, “Pacific Rim” trailers have continued to surface in the show’s first ad break, a position often viewed by sponsors as more desirable. A Warner Brothers spokesman said the studio declined to comment.

CBS started pitching “Dome” to potential sponsors in March, Ross said, enlisting CBS Entertaiment prexy Nina Tassler to help explain the drama and its appeal. CBS told advertisers the show was likely to draw a very broad audience and could attract viewers between the ages of 18 and 49 – the demographic advertisers covet the most – in significant fashion. “Dome” tells the improbable tale of a small town snared under an unbreakable dome of unknown origin, and its sci-fi pedigree – one of its producers, Brian K. Vaughan, did a stint on ABC’s “Lost” and also writes comics – may be snaring viewers who don’t normally tune to CBS stalwarts like “NCIS” or “The Good Wife.”

In its first three weeks, “Dome” has been a success for CBS, which is betting that a special-effects –laden scripted drama can bring viewers back to broadcast TV during a time when many abandon it. For years, broadcast networks have accepted the audience declines and aired reruns, reality shows and lower-quality programming. But recent ratings for “Dome” would appear to suggest there is an audience in June, July and August. The first episode of the series, based on a Steven King novel and exec produced by Steven Spielberg, reached 13.53 million same-night viewers, and 16.7 million with three days’ worth of DVR playback included, according to Nielsen. Last night’s episode reached 10.6 million viewers during its 10 p.m. time slot, according to preliminary figures.

Movie ads are more often associated with Fox, which skews heavily toward younger viewers who typically attend movies most heavily. Indeed, CBS is winning the attention of Hollywood marketers despite having the highest median age among the English-language broadcast networks for its viewers, according to ad-buying agency Horizon Media. The median age for a CBS viewer was 56.8 in the 2012-2013 season, while the median age of a CW viewer was 43.5, the lowest.