It says in the Gemara that we can say Shma until the third hour since that's when kings get up. What kings are we talking about? Jewish kings weren't around until much later, so Sof Zman Krias Shema ...
In Berachoth (3a) a Beraitha states that there are 3 reasons not to enter ruins - that it is unseemly, that walls might collapse, and that unsavory characters might lie in wait and harm the person. ...