[Mishnah Tamid 3:8][1] lists a bunch of things in the Temple that could be heard all the way in Yericho.

Some of the things: the gate opening, the Levi'im singing, the Kohein Gadol on Yom Kippur, smelling the *k'toret*.

Now, could these really reach all the way from Yerushalayim to Yericho? Were they just really loud, was it a miracle, or perhaps the Mishnah is exaggerating.

The distance is [apparently][2] around 15 miles (25 km).


  [1]: http://www.sefaria.org/Mishnah_Tamid.3.8
  [2]: https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&es_th=1&ie=UTF-8#q=distance%20between%20jerusalem%20and%20jericho&es_th=1