By Cid, from http://lounge.moviecodec.com/vs-general/las-noches-size-158036/
It all depends on which gate they started at... Average walking distance (you can’t prove they would WALK faster than average) would be around 215 miles in 72 hours. Then you have to deduct roughly 18 hours for sleep. (assuming they only got about 6 hours a day) And a little over an hour a day for breaks and whatnot (just to be fair) and you’d come up with around 50 hours for walking. According to Google Maps, you can walk 150 miles in 50 hours. That’s roughly 3 miles per hour.
Now, if I recall correctly, they were on the corner of Los Noches when Neil pointed and said the closest gate is that way. We’ll just assume for consistency that there would be a gate in the middle of each wall. (you really don’t want there to be more than one gate because it really just makes it much larger) She’d be pointing to the short end of Los Noches and basically saying the middle of the wall is 150 miles that way. So you have 300 miles for the total length of the short side.
http://i3.mangapanda.com/bleach/351/bleach-2402627.jpg
Just judging by this panel, Los Noches' long side is at least 3 times longer than the short. So basically the long side is around 900 miles.
Giving you a square footage of roughly 270,000 miles. Or roughly 434,000 km. So basically the size of Texas. Even if you cut down drastically... Giving them only 25 hours of walking instead of 50, it’s still half the size of Texas. You’re looking at a huge structure no matter how you slice it.
End of Cid's post
And Lanza dwarfed Las Noches. By a huge amount. Its at least 4 times larger then LN, if not more, you could probably stack up four LN's on top of each other and get the height of Lanza.......Do the math....unless I have to.
The fact of the matter is, destruction level aside, Lanza is incredibly fast.
Lanza, which was fired somewhat from the middle of Las Noches. Please note that it’s impossible to tell where they are, but it’s definitely still near the spot where that shockwave hit. However, they were definitely still in Las Noches circumference.
So Lanza travelled all of this:
http://i3.mangareader.net/bleach/351/bleach-2402625.jpg
http://i3.mangareader.net/bleach/351/bleach-2402627.jpg
In a time-spam this short:
http://i20.mangareader.net/bleach/351/bleach-2402629.jpg
No matter how you put it, the max number of seconds it would have taken would be about 4.
That is astoundingly FAST