Love Downton Abbey? Hightail it to Highclere Castle. Is knitting your thing? Trek the world shopping for unique yarn.

While an archaeological dig used to define themed travel, these days you might hop a cruise based on your obsession with Lord of the Rings, miniature model villages, even a cult author - bringing like-minded people together and offering bragging rights as well.

As travel agencies looked for ways to regain revenue lost when U.S. airlines cut commissions in 2002, and reality TV exposed would-be travelers to the far corners of the world and far crazier things to be done there, themed trip offerings have proliferated.

Maria Stefanopoulos, an avid reader and sports fan, launched Ingenious Travel in 2006, and since she added themed vacations three years ago, calls for these kinds of trips have grown from about one to two a month to four a week.

The L.A.-based company offers an annual 50 Shades of Romance conference (featuring workshops with erotic romance authors and a screening of 50 Shades of Grey), and a Jane Austen tour in England with writer Syrie James, both costing about $3,000 without airfare.

Author cruises - "a book signing on steroids" - give fans a chance to get to know the author as a person, not just as a writer, Stefanopoulos said.

"If you have a theme that everyone is interested in, it makes the bond tighter."

Sandi Byron, 67, agrees. The knitter from Horsham has been on seven craft cruises where she takes courses from expert knitters and travels the globe "yarn crawling."

"It's the best way for a single person who knits to be able to cruise on her own," said Byron, who has traveled to Hawaii, Ireland, Alaska, and the Christmas markets in Germany, Austria, and Hungary, all run by Craft Cruises out of Steamboat Springs, Colo. Byron chooses to room by herself and spends about $4,000 plus airfare for trips that average two weeks.

Thomas and Ann Howell started excursions, mostly to Africa, in the late '70s with the Philadelphia Zoo. After moving from Bucks County to Reno, Nev., in 2002, the couple began creating personalized biannual guided tours focusing on bird sightings.

"Having your own guide to yourself means you go wherever you want, stop forever how long you want to see whatever you want," said Thomas. "That spoiled us for the rest of the trips."

With the help of Premier Tours in Philadelphia, they have toured Botswana, Malawi, KwaZulu-Natal, and other African nations in search of new birds.

"When you have some interest that really absorbs you, it makes for a much better experience," said Ann, who is in her 70s. "I've been bored on a lot of other vacations. With birds, I'm never bored."

Premier Tours, in business for 20 years, focuses solely on Africa and the Indian Ocean islands, with trips priced from $5,000 to $10,000 per person, but President Julian Harrison has noticed a shift in consumer interests in the last 10 years.

"People don't want to do the stereotypical safari where you sit in a vehicle all day and see animals," said Harrison. Instead, travelers want to be more engaged, with guided walking tours or an elephant-back, horseback, or mountain-biking safari. Harrison attributes the change to people seeing these opportunities on the Internet - " 'That looks like fun. I want to try it myself.' "

When Viator, a Web and app-based tour company, began arranging tours in 1995, a themed vacation was a visit to the tallest building in a town - the Empire State Building, the Eiffel Tower, or the Sears Tower in Chicago, said Kelly Gillease, vice president of marketing.

In the last couple of years, "with the prevalence of interesting shows and epic saga movie series, people are more interested in traveling to the destinations where they took place."

The trend started shortly after 2001's Lord of the Rings: The Fellowship of the Ring was released, followed by The Hobbit, she said. "You can visit Hobbiton in New Zealand; the set is still there, and the tours are still popular."

So is a visit to the home of the Earl and Countess of Carnarvon (a.k.a.  Downton Abbey) in Hampshire, England, with the number of tourists growing 180 percent year over year. And it's tough to book. "People live there, so only a limited number of visitors are allowed to go through," Gillease said.

Game of Thrones is even hotter, with tours in Dubrovnik and elsewhere in Croatia growing more than 300 percent this year over last year. "The culture around television, movies, and celebrities has increased over time, and getting a little piece of that is very exciting to people," Gillease said. In addition, "it's easier to travel to a lot of these places than it used to be."

Viator runs tours to complement a theme, from a couple of hours (Highclere Castle, for instance) to several days (touring holy sites in Israel), with prices ranging from $73 to about $1,000, not including airfare.

For travel alone or with others, themed vacations connect travelers with people who have similar interests. Your best friends, after all, may not have your appetite for the making of fine, dark chocolate.

If there's a downside to these kinds of vacations, people might overlook some worthy aspects of their destination because they are unrelated to their theme - say, they miss the Eiffel Tower while on a French wine tour.

Of course, more than 250 million people can say they have looked out onto Paris from the top of that iron latticework icon, but not many can say they walked in Carrie Bradshaw's shoes in Morocco.

"People are craving unique experiences," said Amanda Kendle, travel blogger at Australia-based NotABallerina.com. "And now that normal kinds of travel have become so much easier, they are searching for a way to make their travel special for personal gratification and for the interest factor in telling others."