Explanation
Emphasizes that something is to the extreme; 'you have no idea how...', 'it's incredibly...'.
Formation
Verb-casual + といったらありゃしない / い-Adjective + といったらありゃしない / な-Adjective + だ + といったらありゃしない / Noun + だ + といったらありゃしない
Detailed explanation
The ～といったらありゃしない grammar point is an idiomatic expression used to emphasize that something is extremely or incredibly a certain way—often beyond words. It can be loosely rendered as 'you wouldn't believe how...' or 'it's indescribably...'.
Examples
Sono mise no ramen wa oishii to ittara arya shinai.
You have no idea how delicious the ramen at that shop is.
Kanojo no ryouri no udemae wa jouzu da to ittara arya shinai.
You have no idea how skilled she is at cooking.
Kono fuyu no samusa wa kibishii to ittara arya shinai.
You have no idea how harsh this winter's cold is.
Sono shousetsu wa omoshiroi to ittara arya shinai.
You have no idea how interesting that novel is.
Practice
Grammar content sourced from hanabira.org.