As the people of Wales celebrate one of the most important dates in the Welsh calendar, St David’s Day (March 1), Visit Wales joins the patron saint’s celebration with suggestions for some great places to see in this historic and picturesque part of the British Isles.

1. Visit a castle

There are more than 600 castles in Wales: more per square mile than anywhere else in the world. For fairytale turrets, head north of Cardiff to 19th century Castell Coch.

In mid-Wales, historic Harlech Castle in Cardigan Bay saw the longest siege in British history from 1461-1468, while in North Wales, visit opulent neo-Norman Penrhyn Castle and see a one-tonne slate bed that was made for Queen Victoria.

2. Trampoline in a slate mine

At Bounce Below, you can unleash your inner child on giant trampolines, walkways, slides and tunnels made of netting in a 176-year old disused cavern.

3. Be dazzled by beauty

The UK’s first designated Area of Outstanding Natural Beauty (AONB) was the Gower Peninsula in South West Wales.

Visit Rhossili Beach, which recently came third in TripAdvisor’s Top 10 Beaches in the World, and when the tide’s out walk to Worm’s Head to spot seals and seabirds.

[Read more: The cross-country road trip that made me fall in love with Wales]

4. Walking Wales

The first country to offer a dedicated footpath around its coastline, the Wales Coast Path covers 870 miles of varied and beautiful landscape.

Add Offa’s Dyke, a path along the Welsh-English border, and you circumnavigate the entire country.

Or just dip in wherever you please: the Pembrokeshire Coast Path in South West Wales is particularly picturesque, or you can spot dolphins from the Ceredigion sections in mid-Wales.

5. Pray for rain…

…and be in the right place to enjoy it.

Waterfall Country in the Brecon Beacons is especially fun following a downpour. Don’t miss Sgwd Henrhyd, which featured in The Dark Knight Rises as the entrance to the Batcave, and walk behind a curtain of thundering water.

6. Go wildlife watching

Just off the coast of Pembrokeshire, West Wales, Skomer Island is unlike anywhere on earth.

Stay there in July and hear the incredible night-time symphony of thousands of Manx shearwater birds returning to the island after hunting.

In autumn, watch Atlantic grey seals make their way home to give birth, and coo over cute puffins from May to July.

[Read more: 5 of the best birdwatching holidays in the UK]

7. Catch some waves inland

The first of its kind, Surf Snowdonia is an inland lagoon set in the picture-perfect Conwy Valley in North Wales. Add a two-metre wave peeling over the surface for more than 150m and you have a surfer’s dream.

8. Go to the best book, food, music and… Elvis festivals

Wales really likes to celebrate, be it writers and great literature at the Hay Festival, mid-Wales, , all things edible at the Abergavenny Food Festival, Mid Wales,

or music and dancing in fantastical Portmeirion, North Wales, at Festival No. 6.

But an event to clear your calendar for has to be the Elvis Festival, Elvies, in Porthcawl, South Wales, an annual celebration of The King – and the biggest of its kind in the world.

9. Tick off 200 listed buildings

Conwy in North Wales is one of the best preserved medieval fortified towns in Britain, with over 200 listed buildings that date from the 14th to the 18th centuries including the splendid Conwy Castle.

It’s also home to Britain’s smallest house, which measures just 10ft x 6ft.

10. See Britain’s smallest city

A place of beauty, peace and pilgrimage, St Davids is the smallest city in Britain with a population of just over 1,600. Named after the patron saint of Wales, the roots of St Davids go back to the 4th century when St David himself lived here.

With some of the most magnificent coastal scenery in Pembrokeshire, this is the heart of the Pembrokeshire Coast National Park.

With splendid sandy beaches, spectacular wildlife and streets alive with shops, galleries, pubs and restaurants, St Davids is also home to one of Wales’ great cathedrals, the site of the shrine that holds his name.

Which places do you think are Welsh must-sees? Tell us in the Comments section below.