ideal
... that unlike their Euclidean equivalents, the ideal regular tetrahedron, octahedron, and dodecahedron can all tile hyperbolic space ?
... that unlike their Euclidean equivalents, the <b id="mwBSg"><a href="./Ideal_polyhedron" id="mwBSk" rel="mw:WikiLink" title="Ideal polyhedron">ideal</a></b> regular tetrahedron, octahedron, and dodecahedron can all tile <a href="./Hyperbolic_space" id="mwBSo" rel="mw:WikiLink" title="Hyperbolic space">hyperbolic space</a> <i id="mwBSs">(pictured)</i><span about="#mwt72" data-mw='{"parts":[{"template":{"target":{"wt":"-?","href":"./Template:-%3F"},"params":{},"i":0}}]}' id="mwBSw" style="padding-left:0.15em;" typeof="mw:Transclusion"><span typeof="mw:Entity">?</span></span>