Yhyjyk

One of my favorite poets is probably Guillaume Apollinaire. His story and proximity to Picasso made him a precursor. Calligrams was a constant attempt to merge poetry and visual. I am wondering how we could actually recreate in TikZ

This is just to mention that TikZ has already built in a large selection of tricks that can be applied to paths. Here is a very basic example. (Yes, I know I am not a poet.;-)

documentclass[tikz,border=3.14mm]standalone
usetikzlibrarydecorations.text
begindocument
begintikzpicture
defmypath
 (-2,0) to[bend right=10] (0,5.1)
 to[bend right=10] (2,0) -- (1.5,0) -- (0.8,1) -- (-0.8,1) -- (-1.5,0) -- cycle
draw mypath; 
path[decorate,decoration=text along path,
text=In Paris there is a tower and beneath it there grows a flower. And often
on Mondays there is a shower.] mypath;
endtikzpicture
enddocument

The IMHO most stunning tools are however not from the pgfmanual, but due to Paul Gaborit's great answer. You basically define the contour and the macro takes care of the rest. (Of course, you may want to tune things in the end a bit, but it is stunning how much it does out of the box.)

documentclassstandalone
usepackagelmodern
usepackage[T1]fontenc
usepackageshapepar
usepackagemicrotype
usepackagelipsum
usepackagetikz
usetikzlibrarycalc,fit,intersections

defshapeparnodeaccuracy2
newcommandshapeparnode[6][]
 % 6 parameters:
 % style for node (default:empty),
 % h margin, v margin, left path, right path, text (just one paragraph!)

 % name left and right paths and compute there bounding boxes
 beginscope[local bounding box=leftbb]
 path[name path global=left,xshift=#2] #4;
 endscope
 node[inner ysep=-#3,inner xsep=0pt,fit=(leftbb)](leftbb);
 beginscope[local bounding box=rightbb]
 path[name path global=right,xshift=-#2] #5;
 endscope
 node[inner ysep=-#3,inner xsep=0pt,fit=(rightbb)](rightbb);

 % global bounding box
 path let
 p1=(leftbb.north west), p2=(leftbb.south west),
 p3=(rightbb.north east), p4=(rightbb.south east)
 in
 pgfextra
 pgfmathsetmacroymin(y1 < y3) ? y1 : y3
 pgfmathsetmacroymax(y2 > y4) ? y2 : y4
 typeoutymin ymin
 typeoutymax ymax
 node[inner sep=0,fit=(x1,ymin pt)(x3,ymax pt)](mybb);

 % compute nb steps
 path let p1=(mybb.north), p2=(mybb.south) in
 pgfextra
 pgfmathsetmacrofnthght1em/shapeparnodeaccuracy
 pgfmathtruncatemacronbsteps(y1-y2)/fnthght
 xdefnbstepsnbsteps
 typeoutnb steps nbsteps
 ;

 % horizontal references
 path (mybb.north) -- (mybb.south)
 foreach cnt in 0,1,...,nbsteps
 pgfextrapgfmathsetmacroposcnt/nbsteps
 coordinate[pos=pos] (ref cnt)
 ;

 % left and right boundaries coordinates
 foreach cnt in 0,1,...,nbsteps- ref cnt);
 % same line from right to left
 path[name path=rtol]
 (mybb.east 
 % start point (and initial value of boundshape)
 path let p1=(l 0) in 
 pgfextra
 pgfmathsetmacroxstartx1
 xdefboundshape00bxstart
 xdefxminxstart
 xdefxmaxxstart
 ;

 % top and bottom
 path let p1=(l 0), p2=(l nbsteps) in
 pgfextra
 pgfmathsetmacroystarty1xdefystartystart
 pgfmathsetmacroyendingy2xdefyendingyending
 ;
 % incremental definition of boundshape
 foreach cnt in 0,1,...,nbsteps
 path let p1=(l cnt), p2=(r cnt) in
 pgfextra
 pgfmathsetmacrostartx1
 pgfmathsetmacrolenx2-x1
 pgfmathsetmacroyposcnt/nbsteps*(ystart - yending)
 let\=relax xdefboundshapeboundshape\ypoststartlen
 pgfmathsetmacroxmin(xmin < start) ? xmin : start
 xdefxminxmin
 pgfmathsetmacroxmax(xmax > start + len) ? xmax : start + len
 xdefxmaxxmax
 ;
 
 % draw the node with text in a shapepar
 pgfmathsetmacroymaxystart - yending
 let\=relax xdefboundshapeboundshape\ymaxe0
 node[#1,text width=xmax pt - xmin pt,align=flush left,
 anchor=north west,inner sep=0]
 at (mybb.north west -

defmytextIn Paris there is a tower and beneath it there grows a flower.

begindocument%
 begintikzpicture
 defpathone(0,1) -- (-0.8,1) -- (-1.5,0) --
 (-2,0) to[bend right=10] (0,5.1)
 defpathtwo(0,5.1)
 to[bend right=10] (2,0) -- (1.5,0) -- (0.8,1) -- (-0.8,1)
 fill[top color=lime,bottom color=orange,middle color=yellow,draw=white]
 pathone -- pathtwo -- cycle;
 defpathone(0,1) -- (-0.8,1) -- (-1.5,0) --
 (-1.6,0) to[bend right=10] (0,4.1)
 defpathtwo(0,4.1)
 to[bend right=10] (1.6,0) -- (1.5,0) -- (0.8,1) -- (-0.8,1)
 shapeparnode[text=black,font=footnotesizescshape]
 0.1em0.1empathonepathtwomytext%
 %draw[orange] pathone;
 %draw[orange] pathtwo;
endtikzpicture
enddocument