Medjugorje sits in good day-trip country. Mostar and its rebuilt Ottoman bridge are about 25 km and 30 minutes north -- easy to do in a morning, with time for lunch by the Neretva. The Walled Town of Pocitelj, a stunning hillside Ottoman village with a fortress and minaret, sits 30 km southeast and combines well with Mostar.
For something cooler and greener, Kravica Waterfalls are 15 km west on the Trebizat river -- a wide curtain of falls dropping into a swimmable pool, busy in summer. The Franciscan monastery at Zitomislici, 10 km north, has fifteenth-century frescoes and a graveyard with ottoman tombstones.
Across the border, Dubrovnik is 130 km south (around 2 hours) and Split 170 km north -- both are reachable as long days from Medjugorje, but better as overnight stops.