You must construct ASCII Pylons!

PowerShell, 73 bytes

' '*48;46..0|%{" "*$_+-join[char[]](($x=79-$_)..($y=$x+$j++)+(++$y)..$x)}

Try it online!

Outputs the first whitespace-only line, then loops from 46 to 0. Each iteration, outputs the corresponding number of spaces and then a -joined together char-array of the appropriate symbols, via some calculations.

Charcoal, 13 bytes

Ｅ⁴⁸⮌✂γι⊕⊗ι‖Ｏ←

Try it online! Link is to verbose version of code. Explanation:

 ⁴⁸             Literal 48
Ｅ               Map over implicit range
      ι  ι      Current index
        ⊗       Doubled
       ⊕        Incremented
     γ          Printable ASCII
    ✂           Slice
   ⮌            Reverse
                Implicitly print each slice on separate lines
          ‖Ｏ←   Reflect with overlap

Python 2, 73 bytes

i=48
while i:i-=1;r=range(79-i,127-i*2);print' '*i+bytearray(r+r[-2::-1])

Try it online! Crossposted from anarchy golf (see my submission).

Quick post-mortem analysis: xnor and dianne discovered the exact same solution. ebicochneal submitted a 71 byte solution which mitchs improved to 70 bytes. They avoid dealing with bytearray (which is long) or ''.join(map(chr,…)) (which is even longer) entirely, by keeping a "current line" variable and cleverly updating it.