Ticknock Fairy Castle Loop

Those who frequently climb this 6-km (4-mile) trail don't let the icy mountain air or their aching calves stop them.
Ticknock, the most well-known peak in the Dublin Mountains, rewards climbers with breathtaking vistas when they overcome their muscle cramp (making up for the less-than-magical Fairy Castle itself along the way).
Bring a flask of hot whiskey to treat yourself, just like the locals do.

For food after a trek, go to Johnnie Fox's in Glencullen, Ireland's tallest pub (and take the bus back home).