We enjoyed Costa Rica when we went there several years ago.
Depending on your budget, you can find a lot of interesting sites to visit... for instance, you can tour European henge sites (here's a site with a
lot of info, and there are a LOT of henges and megalith sites around. In England, if you can read Ogham runes, you can find some ancient writings
(300 AD to around 600 AD) on stone that you can tie into your tours:
There's a number of sites in Europe with cave paintings as well -- France is particularly famed for these.
Here in America, I think it's a lot of fun to go visit petroglyph and pictograph sites (just google for them. My favorite is the Fate Bell shelter
here in Texas, the White Shaman site in Texas (mainly because it's HARD to get to and not that many people have seen it) and the wonderful Painted
Rock and the caves of the Chumash in California.) Canada also has some interesting sacred sites, medicine wheels, and tribal areas -- though it can
be depressing (as it is here in America) to see how much of their knowledge and culture they've lost.
Oh... Deer Valley in Arizona is also a good one to visit. In fact, you can do a good ancient site tour simply doing America's southwest.
Hawai'i has some wonderful petroglyphs and pictographs, but FINDING them is another matter. We found several, including that of Kapua and the ones
in Volcano National Park. Expect hikes and vague info, but part of the fun is actually locating them (good detective work is needed.)
Australia, of course, has excellent sites -- as an English speaking tourist you can't get into too much trouble out there.
Riskier areas are places where you don't speak the language as well as a native speaker. This is where you need to do your homework (some areas of
Mexico are notorious for kidnappings and robbers who prey on tourists, for example, while others are perfectly safe.) If you don't have friends or
contacts who live in the country you're interested in visiting, there are a couple of ways you can have adventures without getting into too much
trouble (some areas, frankly, are dangerous for foreigners.)
* contract with local tour companies and make your own tour. This is what we did in Costa Rica through our (local) travel agent. Having someone
drive you around means less getting lost, better dealing with emergencies (we had roads closed off because of landslides... we would have NEVER
figured out that "darrumba" meant "landslide"), and that you arrive at your place of adventure (we were touring volcanos) feeling a lot fresher
and ready for the 3 mile hike uphill.
* Go along with one of the citizen science expedition groups. You'll work hard, have fun, and learn a LOT of stuff! Here's a couple of typical
tour companies, but you can easily find more:
(BTW, any local college/university will have flyers for various tours like these)
Or go visit Dracula's haunts: www.enzia.com...
The student tours here look fun though the site is outdated. Still, the names would give you a good idea of where to visit in the US:
Canyon de Chelly (this is on our "gotta visit!" list): www.footpathjourneys.com...
If Egypt's a consideration, this site is a good starting place (and has excellent resources for helping you find some of the less-visited monuments):
And of course India is full of sites, as is the whole region. The temples of Sri Lanka look fascinating as well.
First thing to do is sit and figure out a budget, then pick an area preferably with a language you already know OR with a language you feel you can
learn (Spanish, for us.)
Another thing to google for is 'archaeoastronomy' where you can visit ancient observatory sites. Those are always interesting to add to a tour, but
you have to time your visit to dates that the builders found significant.