"Think about that statement. 80 percent of the sky blocked by terrain. I suggest you go outside and look around. Now visualize 4 5ths of the "sky" blocked by "terrain". You would most likely be at the bottom of a sharp walled canyon. Pretty un-freakin likely. And certainly not the public image of a lunar dome. Why the aversion to underground? You could always go up to an observation bubble for "scenery". "
I said:
"If you build in area which has 80% of total sky blocked by terrain then you will only receive 20% of the Cosmic rays"

I said "total sky".
If you were in Kansas with horizon below your ankles you aren't going to see 50% of total sky- or even if you are on Mt Everst same deal. You would need to be in space (in orbit) to see 50% or more of sky. And I don't mean without turning your head and looking around- in "one glance" you will never see 50% of total sky no matter where you were.
If you are "standing" next to any large object (say a barn) it all by itself blocks out about 50% of "total sky". So as far as visually having 80% of total sky blocked isn't a big deal. If you design your building so it has large windows facing the right direction, then your tourists are going to see lots of sky.
As far as being in "the bottom of a sharp walled canyon". Take a crater, say it's 5 miles in diameter and say it's walls are fairly steep and rise 500 feet or so and the crater floor is fairly flat. If you are in the crater you CAN see most of the sky if you are standing in the middle of crater, but without turning your head (tilting your head back) you will see the most sky if you are near the rim walls. Near rim walls has least "total sky" but can give tourist best view of sky in the crater. Now if locate the building in good spot and design the building well, then you can provide a great view and have your cosmic rays blocked. Now, as far as exactly how the building is built depends on location- any good architect wants to see the location before designing a building.
But generally you wouldn't need to be limited to living in some dark hole- in right location you can have both Sunlight and Earthshine lighting your landscape plus have the nightsky and not live with any danger of radiation.