Children's book ID request

No idea, sorry. You could try here http://groups-beta.google.com/group/rec.arts.books.childrens

They're usually pretty good at book IDs. Hey, on the subject, I read a book in the early 80's that I'm trying to ID. Kids book, young man on a quest kind of thing, he goes to various cities around the country solving problems. The three I remember are -
Ecumene, a town full of churches that move through the city on criss-crossing tracks, knowcking down houses and sometimes colliding. He solves the problem by steering all the churches into the main square, where they all collide and form one big church.
Some town beside a mountain, where every year (ten years?) this guy comes down and steals a kid which he throws into a chasm. He reveals that the town is balanced on the edge of the chasm, and without the sacrifice of a kid each year it will fall in. In the end, the child-stealer throws himself in, because one willing sacrifice will save the town for 100 (1000?) years.
Some other place, with a stone throne on a hill, where if you sit on the throne and watch the sun go down/come up, and aren't worthy/the rightful king, you die.
Anyone any ideas?

I'm trying to place a children's sci-fi book where at some point the kids and some other adults get trapped in their own house by a gang, possibly a government gang, in the middle of nowhere. A few adults go out to talk sense into them, and are shot down. Later that night, a couple of other adults go out to surrender, and die mysterious and bloody deaths. Later, the people left inside figure out that there aren't any guards there any more, there's just a security measure outside the door where if anything passes through, bolts shoot out at knee height and chest height. I particularly remember one of the people demonstrating this by picking up a chair and holding the legs while showing that the holes cut in the back were always at the same height. So a kid has to crawl out, and... there my memory fails me. I doubt I'd even read it a second time, but the image sticks with me, and I wouldn't mind a name.

I have been trying to figure out what that book is for years! A teacher read it to my class, and I remember completely losing myself in the fantasy.

Love this thread but I'm afraid I don't know any of the above. Pls post more!

You could also try asking at a specialty bookstore. After years of searching for a book based on one recollected scene, I walked into B00ks of W0nder and posed the question and someone said "gosh, that sounds like Steel Magic by Andre Norton" and I was home free.

I recommend http://loganberrybooks.com/solved-s.html

They're really good at tracking them down. Also, although it's not the easiest to navigate, I've found several titles through their database of "solved mysteries."

Also, please post the answers when you find them -- inquiring minds might read the recovered titles.