Look into Carey's Castle in JTNP on localhikes.com
Although to get there its off the 10 fwy, not the main park entrance. Also you'll need to GPS your way or be really good at following instructions with a map. Very easy to take the wrong canyon.
read the localhikes.com trail reviews to get an idea on what to expect, and look for the GPS waypoints around google.
its a sandy canyon, very minor boulder climbing, if you can climb on your desk you will be fine.
no rope or special skills required.
leave the hiking poles at home, they will get in the way.
thorns are present in some places, so don't be a hippie. wear boots, not sandals.
bring some tweasers or multi-tool pliers to pull the inevitable cactus thorn out of your boot. my friend wanted to smell a cactus flower and got a thorn on his nose. DOH!
a fun thing to do with those giant 45 degree leaning fallic-looking cactus, is to pose with it between your legs, and take a silly photo that will be used against you when you run for government office.
Careys Castle has double history.
first it was an ancient indian area, evidence of metate grinding stones.
inside the castle, you can see some faint indian petroglyphs. very faint, if you look upside down.
then in 1940s a gold mining prospector did a neat job with masonry to build his shelter, and water system. there is chicken wire fence, and a rusty egg beaters.
There is a closed mine entrance nearby.
and a small monolith headstone, probably someone is buried there, I'm not digging it up.
there's some rusted out artifacts in the "castle"
my friends got some ghost apparitions on the digital photos inside the shelter, but I think it was just the way the light bounces.
There are plenty of mouse droppings inside, and a rusty old bed.
There used to be girlie nudie mags from the 1940s, but they've been snaked out by hikers.
The park rangers will try to discourage you from going to careys castle, for 2 reasons:
1) it's a part of the park that doesn't require payment since there is no ranger entrance, I think it's a Edison road.
2) in case you get lost, its on the opposite side of the park for them to rescue someone who didn't pay an entrance fee.
This is do-able on a day trip, granted its a long ass drive from LB or OC to JT. but if you do camp there, you can explore around, and the sunrise / sunset photos are amazingly rich in color, like a tequila sunrise drink orange red yellow etc.
every time I have been there, no one was around, although the footprints in the sand point to a lot of traffic.
if there is a chance of rain, remember that you are in a canyon. hint: flash flood.
lastly, don't follow the footprints. lost people also leave footprints.
There is a spot halfway, where the trail looks like it turns left, and going forward is impassable, trust your map and go fwd, climb those rocks and it makes sense afterwards. there are some cairns stone piles along the way. some are misleading too.
the beginning canyon entrance is misleading, depends where you start counting, it's not the second slot, it's the third one to take. again GPS coordinates on localhikes reviews,
http://www.localhikes.com/Hikes/CareysCastle_4472.asp
http://ronslog.typepad.com/ronslog/2007/03/careys_castle.html
http://dzrtgrls.com/careys_castle/careys_castle.htm
look on flickr for photos. but if you learn too much, you'll spoil the adventure for yourself.
the national geographic map is useless. it just shows this place as a random X on the map, and it's not even accurate.