A common knock against the official Third Imperium setting for GDW's Traveller is that it's simply too big. Encompassing 11,000 worlds spread over nearly 300 subsectors, there's simply no way a referee can make use of it all except in a cursory way. Even a single sector, like the Spinward Marches or Solomani Rim, still contains close to 500 planets. The end result is that, for all its breadth and diversity, the Third Imperium will be little than an abstraction in most campaigns that make use of it.
There's more than a little truth to this criticism, though, at the same time, I also feel that using the Third Imperium as a loose backdrop is exactly what the referee should be doing. Focusing too much on large scale sector-wide events, like the Fifth Frontier War, is precisely where GDW went wrong in its later development of Traveller. In my opinion, the company – and the game – would have been much better served by focusing instead on smaller scale details, such as individual subsectors or even worlds.
While the much celebrated The Traveller Adventure did the former, 1983's Tarsus: World Beyond the Frontier did the latter and did it very well indeed. Located in the unaligned District 268 subsector of the Spinward Marches, Tarsus is a non-industrial, agricultural world that's home to some 2.2 million human beings. Consequently, it's something of a backwater planet, though it maintains economic ties to both the Imperium, which it hopes to join one day, and other nearby interstellar powers, like the Sword Worlds.
Tarsus was released as a boxed set and included a 24-page World Data book (written by Marc Miller and Loren Wiseman) that detailed the planet, its history, local government, ecology, and more; a color map of the planet; a color map of an important region of the planet (Tangle Wald); a map of District 268 subsector; five 4-page adventure pamphlets; and a dozen pre-generated character cards. It's an excellent collection of material, attractively presented. Taken together, the referee has more than enough information to provide many months' worth of adventure on Tarsus itself, even longer if the characters eventually expand their scope beyond the planet itself to its neighbors in the subsector.
With its focus on agriculture and ranching nobbles (a large, horned, grazing animal), Tarsus has a vaguely Western feel to it. The whole planet reminded me of an unincorporated territory of the 19th century United States, on the verge of consideration for statehood, with various interests lobbying one way or the other. Indeed, there's much discussion of the voting system employed on Tarsus, which not only allows the open buying and selling of votes but also the buying and selling of them by newcomers to Tarsus. By law, only individuals can hold votes, though they may hold multiple votes, and may freely vote on behalf of others, like offworld corporations, that cannot themselves legally vote. It's a situation ripe for political machinations and corruption – not to mention adventure.
Of course, there's more to Tarsus than political maneuvering. The planet is a giant sandbox, with plenty of scope for a variety of approaches to its content. Player characters could, for example, become involved in nobble ranching, working for or against a megacorporation, exploring the Tangle Wald, cataloging the planet's native life, and more. There are also several flashpoints for armed conflict, as well as mercenary company in need of new recruits. This is in addition to the presence of many local patrons, a staple of Traveller adventures and a good way to kick off a campaign or extended adventure on this frontier world.
If one were to complain about Tarsus, it's that the information it presents about the planet and its conflicts is diffuse. The referee needs to read through all the included material several times to get a good handle on it, but, to my mind, that's the job of any good referee. Having done so, the referee should have little trouble keeping things the players and their characters engaged for a long time. With so many worlds in the Third Imperium, Tarsus is thus a good example of the kind of thing I wish GDW had done more often: fleshing out a single world in sufficient detail to demonstrate how much fun could be had be spending an extended period of time there. The game is called Traveller for a reason, to be sure; that doesn't mean the characters should always be on the move, Tarsus is a world worth visiting.