The <a href="https://en.wikipedia.org/wiki/Cave_of_Swallows" id="mwtw" rel="mw:WikiLink" title="Cave of Swallows">Cave of Swallows</a>, the largest known cave shaft in the world, is discovered in <a href="https://en.wikipedia.org/wiki/Aquismón" id="mwuA" rel="mw:WikiLink" title="Aquismón">Aquismón</a>, <a href="https://en.wikipedia.org/wiki/San_Luis_Potosí" id="mwuQ" rel="mw:WikiLink" title="San Luis Potosí">San Luis Potosí</a>, Mexico.