While in the area, it's worth a trek to either end of the Troggy for two very different experiences. Just upstream of the Whirly Pools is Caerwent (Info; Map), which is well worth a visit. The Roman walls of this town are well preserved (Photo of west wall), including the southern wall, known in the 1800's as the "Port Wall". From the south wall you get a good view across the Troggy valley, and it is easy to see the flat section of the valley running up the middle (Photo: flat area between hedgerows) which is likely to be alluvial infill (though may be associated with the alteration of the brook's course when the Severn Tunnel was built: see Science).

At the other extreme, in time and engineering history as much as space, is the current mouth of the Troggy at Calicot Pill (Map; previously it discharged at further east Map¹). If you park in the small industrial estate labelled "The Pill" on the map, you can walk down the Troggy (Photo) to the Severn, where you find yourself under the ominous start of the old Severn bridge, undoubtably one of the creepiest places in Britain and, in some strange way, even wonderful (Photo next to the bridge; Photo under the bridge).