Bloc 4 is located on the opposite side of the road from Blocs 1, 2, and 3. It is in a sheep pasture, so watch your step.
From Haut Poirier we descended from the Rohrbach Plateau to the Saar Valley. There are a number of small blockhouses between the Casemate du Wittring and the town of Saaralbe. Strangely, the P.O. du H-P is located in the SF de la Sarre, rather than the SF Rohrbach. The Casemate du Wittring is the last CORF casemate on the east side of the flood zone; the next is the Casemate Sud du Bois de Laudrefeug in the SF du Faulquemont.
The SF de la Sarre is very interesting and I highly recommend a full day's visit. However, if you are looking for large forts and tunnels, stay away. I suppose what fascinated me the most about this region is the engineering aspect and the diverse elements that are found here: dikes, dams, blockhouses, casemates, reservoirs, STG casemates, artillery casemates, and a curious road barricade.
We began our visit near the town of Holving. On a hill to the SE of the town, near the cemetary, is the Silberg hill, which is dotted with several MOM Blockhouses. Down the hill across from the cemetary is a monument to the defenders of the Sarre Offensive.

This region of the Maginot Line was an afterthought, built after the Saar region was returned to German control in 1935. Void of any defenses, the engineers took advantage of the low-lying terrain crossed by numerous streams which are fed from the Saar and Albe rivers. The land is for the most part, flat, dotted with small hills, which were turned into strongpoints like that of Barst.
The idea was to build a series of dikes and barriers (Barrages), mostly along the Mutterbach Creek. We visited the barrage of Remering on the Mutterbach - due north of the village above the football field. The metal floor of what appears to be a bridge is hoisted up at one end - in this case - the left side - and dropped into the slots in the concrete posts, thus stopping the flow of water.

There are also some larger reservoirs (Etangs d'Hirbach, Marais, Diffenbach, and Hoste, to name a few) from which water could be released to flood this sector. The higher ground was protected by blockhouses and infantry and artillery casemates. One of the hilltop strongpoints is at Barst-Cappel, which consisted of several STG infantry casemates, and one STG artillery casemate for 75mm cannons (not fortress models, but field models).
In the valley to the east of the Barst ridge was a curious anti-tank barrier used to block the road which ran along the base of the ridge. This "wagon anti-char" could be rolled down a short slope on 60cm rails to block the road. A chain pulley system allowed the wagon to be pulled back up the slope to clear the road.
Rails imbedded in the side of the concrete block prevented the bloc from being tipped over. The valley behind would be flooded, preventing passage. Unfortunately, March to June 1940 were very dry months and the water barrage did not work. All in all, the trouée de la Sarre was a fascinating visit, one I would highly recommend. This ended our visit of the 2nd day. From here we spent the night in Metz, in preparation for our visit to the Bois du Cattenom salient on Saturday. Martin decided to spend an extra day with me.