This is walk number 1 in the TopoGuides booklet Le Haut Vaucluse.
Main parking is just below the village. Walk up but do not go under the arch into the village; take a sharp left following the sign Accès au Château. After about 100 metres there is another Accès au Château sign on a lamp-post on the left pointing to a path up on the right. This is decision time. You can either go up and over – great views, sense of achievement, uninteresting château – or round the hill next to you. If former, as recommended by the TopoGuide, go on up the path and follow it to the top, pausing at a couple of terraces on the way. Circle to the left of the château and once beyond the walls follow the path off to the left down the other side. Take care at the bottom, turn left on the first metalled road to get to the signpost Le Terron (point 5 in the guide). First time I did this I turned right which led to an interesting adventure not in the book).
If you have chosen the gentle stroll around the hill on the road you will also arrive at the signpost Le Terron. From here carry on towards Vaison/Le Besson. At the next signpost, Le Besson, keep on the road towards Vaison and Mourchon. After another 400 metres you reach the Mourchon signpost. Turn right here up the metalled track signposted Royère Sourde.
You might accidentally or intentionally carry on along the road for a couple of hundred metres to the Domaine de Mourchon, owned and run by the McKinlays from Aberdeenshire. A quick degustation may help with the navigation but remember to retrace steps to Mourchon.
Follow the track for about 2km. Walking between vineyards you reach a ruined building on your left with a welcome bench by the path. About 200 metres beyond this there is a sign Forêt Communale de Séguret, (point 7 in the TopoGuide). Turn right here and follow the slightly rougher track down and up again until you rejoin a narrow, metalled road Chemin de Constant. Turn right on the road (point 8 in the TopoGuide). After about 300 metres winding down this road the guide book recommends taking a path off the road to the right. There is a sign on the telegraph pole in front of it, a Polish flag on top f a lopsided “L”. (Page 7 in the TopoGuide explains these signs. This means you are on an official, marked way. It doesn’t tell you if you are on the right, official marked way of course). You can take this path but it’s a bit rough; I think they filmed “Game of Thrones” here. It’s a shortcut and rejoins the narrow, metalled road a bit further down the hill – so you can keep to the road if you prefer.
Follow the metalled road to Séguret entering up the Rue Serge Laurens to the terrace and views at Place des Arceaux. Enter the village in triumph through the Portail Neuf (C14th) and avail yourself of the pleasures.
About 8km, 3 hours via the château. About 7km, 2 hours without the climb. There are a couple of restaurants and a gourmet tea shop in Séguret, which is one of the prettiest villages in the area.