There's not much in Portencross – it's just a small hamlet on the Farland Head peninsula 10km down the Clyde coast from the town of Largs... but what makes it special is a quiet atmosphere, a good car park on the seafront next to the castle plus some interesting walks and cycle rides.
From Portencross car park the hamlet itself can be explored including the castle interior (free entry, donations box) with its excellent view from the rooftop – well worth 50 pence :o). Also of interest is the old pier and tiny harbour. A flat walk along a good track heading north beside the shoreline under the magnificent three sister's cliffs leads to Hunterston Power Station and you can continue on the road/path which takes you to Hunterston Sands and Gull's walk.. then return.
An alternative, and the one we took is to climb uphill by taking a path through woods just past the Hawking Crag Pier( the second disused pier walking north along the coastline from Portencross car park.)
This leads up the south side of the Hunterston security fence climbing grassy, sometimes trackless but easy ground until it meets a farm track leading to the summit. The aptly named Goldenberry Hill and the taste is sweet indeed. Great views from here over the Firth of Clyde Islands and the sometimes shimming blue Firth of Clyde. A five star viewpoint at 140 metres high which can be climbed via the easier farm track past Ardneil Farm.( I'd advise people to go up via Ardneil Farm first then come down beside Hunterston as it's far easier going this way and the paths more obvious.) South of Portencross and running straight from the car park a pleasant track leads onto sandy beaches stretching unbroken down to Seamill, almost 3 km away. Popular with families with young children as it's never that busy you can't be alone but frequented enough by other parents and dog walkers it doesn't feel isolated, like some unfashionable beaches. Rock pools and rocky sections lend interest.
The network of small farm roads in this area also lend themselves to cycling , both around the peninsula itself and into West Kilbride, or a circuit past the Crosbie Hills then into Dalry and Kilwinning using mainly back roads or cycle tracks to avoid any traffic. Ardrossan and Saltcoats from here also give a surprisingly nice run on the bike, hugging the coastline all the way before the enjoyable double jewel of promenade and beach cycling at low tide.
For more info on walks and cycle rides throughout this large area- 80 walks and cycle rides, including all the Firth of Clyde Islands: Walking and Cycling Guide to the Clyde and the Firth of Clyde by Bob Law