The Swiss Alps stage the Matterhorn above Zermatt, the Jungfrau Region's Eiger and Mönch trio, the Glacier Express crossing 291 bridges between Zermatt and St. Moritz, and the Bernina Express threading the Engadine.
Hiking peaks with Tour du Mont Blanc and Eiger Trail open, Lauterbrunnen waterfalls full, and cable cars to Schilthorn and Klein Matterhorn running fullest.
Zermatt, Verbier, St. Moritz, and Davos ski December through April, the Matterhorn glacier paradise runs summer skiing, and the Glacier Express threads snow tunnels.
Larch turn gold across the Engadine in late September, alpine cattle descents (Alpabzug) bring decorated cows down from summer pastures, and Zermatt comfortable for slower walking.
Spring shoulder with high passes still snow-bound, but Lauterbrunnen and Lake Lucerne walking accessible by late May, and the Jungfrau Eiger Walk reopening as snow recedes.