4 Islands tour. Krabi's signature day trip — Phra Nang Cave Beach, Chicken, Tup and Poda islands. Longtail-boat tours with lunch start around ฿550 ($16); speedboats cost more but beat the crowds. Book the sunset version if you want the lagoon light without the midday rush.
Railay Beach. Reachable only by longtail boat from Ao Nang, around ฿100 ($3) each way. Railay West is the swimming beach; Phra Nang Cave Beach around the corner is even better. Rock climbers come from around the world for these cliffs — beginner half-day climbs are easy to book.
Ao Nang. The main tourist strip and the smartest place to stay. Beach, night market, dive shops and every tour desk you need. It's a base more than a sight — sleep here, day-trip everywhere.
Emerald Pool and Krabi Hot Springs. An hour inland: a clear green forest pool plus natural warm-water cascades. Usually sold as one half-day tour. Go early — the pool loses its colour once crowds churn the water.
Tiger Cave Temple (Wat Tham Suea). 1,260 steps to a hilltop Buddha with a huge view. Free, but brutal in midday heat — climb at 7 am or after 4 pm. Skip it if knees are a concern; the view from Railay's own viewpoint is a gentler alternative.
Susan Hoi (Fossil Shell Beach). About 15 km from Krabi Town: flat slabs of fossilised shells, laid down roughly 75 million years ago and fused into rock at the shoreline. Free to enter. It's a quick, offbeat stop if you have a car or scooter — skip it if you're short on days, since the beaches and islands come first.
Phi Phi Islands from Krabi. The same famous islands you can reach from Phuket, roughly the same boat time. If you're doing both provinces, take the tour from whichever side has better weather that day.