You can lie on a beach at some Spanish costa for a fortnight. You can 'do' Italy by visiting the usual haunts. You can join thousands of visitors at Munich's Oktoberfest. You can take a selfie in front of the Eiffel Tower. Or you can have a look at these suggestions.
8 islands, 7 climbs, 8 ferries, 7 buses, 5 rental cars (and one bicycle). Lanzarote, Fuerteventura, Gran Canaria, Tenerife, El Hierro, la Gomera, la Palma, la Graciosa: Island hopping of the unusual kind.
For hard-core hikers, there is always the 2,400 km Via Alpina which takes at least 5months to complete. For those with less time on their hands, here's a 7-day itinerary from Tegernsee in Germany to Sterzing / Vitipeno in South Tyrol, Italy.
Scotland's North Coast 500
500 miles (well, 700 actually when counting all the excursions and detours) across the top of Scotland: wild rugged, isolated and impossibly beautiful.
185 miles, ten causeways, 4 ferries and 10 islands; Vatersay, Barra, Eriskay, North and South Uist, Benbecula, Berneray, Harris, Lewis and Bernera. If you can brace the elements, the adventure is yours.