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Anglesey Sea Zoo is an independent aquarium and marine conservation centre on the south coast of Anglesey, near Brynsiencyn. Over 40 tanks show native British sea life, including octopus, lobsters, seahorses, conger eels and jellyfish. Highlights include the No Bone Zone for invertebrates, a wolf fish lair, a real crashing wave, a shipwreck and a kelp forest full of big fish.

Tip: No need to book ahead, as tickets are bought on the door. Standard and family tickets stay valid for 6 days after the day of purchase, so you can return for free in that time.

Plas Newydd is a country house on the north bank of the Menai Strait, with views across the water to Snowdonia. The house has origins in 1470 and was long the seat of the Marquesses of Anglesey.

Tip: Dogs on short leads are welcome in the gardens, but not on the Terraces. Autumn is a busy season for the red squirrels, so stay quiet in the woods.

Bryn Celli Ddu means "the mound in the dark grove". It is one of the best-known prehistoric monuments on Anglesey and is cared for by Cadw. The site began as a henge, a ritual enclosure with a ditch and a circle of upright stones, around 5,000 years ago. A passage tomb was built over it later in the Neolithic.

Tip: Head along the passage into the burial chamber, then look for the replica Pattern Stone behind it.

Beaumaris Castle on Anglesey was the last of Edward I's royal strongholds in Wales, designed by James of St George beside the Menai Strait. Four concentric rings of defences, a water-filled moat with its own dock and a near-perfect symmetrical plan make it a striking sight.

Tip: Use the main town car park opposite for the most direct route in, and watch for two-way traffic there.

Caernarfon Castle is a medieval fortress in Gwynedd, north-west Wales. Edward I began replacing an earlier motte-and-bailey castle with the current stone structure in 1283, and it was built on a grand scale as the administrative centre of north Wales.

The Welsh Mountain Zoo is a zoological garden near Colwyn Bay in Conwy County Borough. It covers 37 acres and has been open since 1963, so it has built up a good range of animal areas over the years.

Tip: Check the zoo's website before you go, as the sources note that animal exhibits such as the sea lions have changed over time.

Penrhyn Castle is a country house at Llandygai, near Bangor in Gwynedd, built in the style of a Norman castle. Thomas Hopper rebuilt it in this Romanesque Revival form between 1822 and 1837, and it is Grade I listed. It is regarded as Hopper's finest work and as one of the most important country houses in Wales.

Conwy Castle was built by Edward I between 1283 and 1287 and is part of a World Heritage Site. Eight large towers and a high curtain wall still stand, and it has the best preserved set of medieval royal apartments in Wales. The ruins are split into an inner and an outer ward, with a Great Hall undercroft and chapels to explore.

Tip: Climb the spiral staircases and walk the full battlement circuit if you can. Cadw highly recommends it.