Towards the bottom of Farndale, the Dove flows into Douthwaitedale and on to Keldholme and Ryedale. There's an obstacle in the way though in the form of the considerable limestone escarpment which is feature of the south side of the moors from Sutton Bank to Scarborough.
Limestone is often rather porous and naturally fissured, if water can get in these fissures it tends to make them wider by erosion and chemical process such as dissolving the calcium way.
This has happened between Ravenswick and HalfWay House and the Dove often runs completely underground when it is not in spate.
Just to the east Hutton Beck also goes below the surface and is thought to join with the Dove underground before they emerge rather spectacularly alongside Bog Hall.
It's relatively easy to access this area as described by York caving club here.
https://yorkcavingclub.org.uk/projects/bogghallcave/index.php
Apparently there is a narrow opening above the obvious outflow through which (with ropes) you can descend into an airspace and if brave enough exit with the water.
It's not possible to go much further upstream but at Hutton Beck they have made a way into the underground passage and were able to follow it some way downstream.
https://yorkcavingclub.org.uk/projects/excalibur/index.php
At the bottom of their web page see the link to youtube where there is video from inside these interesting locations.
I found the dark water surging out felt rather sinister and had no desire to go inside!
