Dun Aengus
I'll close with a lightning round of "ultimates" (what travel writer can resist?): the ultimate medieval walled town in Germany ( Rothenburg), prehistoric stone fortress in Ireland ( Dun Aengus), Riviera town (Vernazza), hike in England's Lake District (Catbells above Keswick), neighborhood pub in London (The Anglesea Arms), castle in North Wales (nope, I still can't pick just one)...and pedestrian market street in Paris (Rue Cler).