graphic show nothing is blocked but sometimes there is invisible wall to prevent me from going, is that a bug or feature?

I see two blue areas on the map, the one above the final bonfire has the item above it, which I assume is the legendary great hammer but I can't find any hidden walls or any way to get there.

i found this area with security things roaming around, but i cannot find any secret? inside this room. i have avoided being seen and tried attacking the walls, all around, and even some pillars. no avail i have also tried getting caught and then dealing with all the enemies. and after you deal with the enemies there are 2 sections of the right most wall that sort of opens up, looks like it could lead somewhere, but even after defeating enemies the security alarms dont go off. no idea what to do, has any...

So, something weird I'm seeing is that there is a complete lack of hitstun on enemies. Or at least there seems to be. I can be mid hit with a great hammer and they can still continue an attack animation. Maybe there is hitstun and its just not evident because of the simplicity of the graphics, but this seems to set the combat up to be very passive. You almost always have to bait the enemy to attack and then go in because you can't stun them. I feel like smaller enemies at the very least should be stunned...

I love the perfect shot of the great bow I love the big slow hitting weapons that do a ton of damage the second i got it was my main weapon until the end is there more weapons with perfect shot mechanics i would like a melee weapon to work the same and be able to perfect shot and perfect hit...