Wooded valley (4)
(Other definitions for glen that I've seen before include "Narrow, deep mountain valley" , "Narrow secluded valley in mountains" , "Depression in Scotland" , "Long narrow valley in Scotland" , "Scottish mountain valley" .)
(Other definitions for dell that I've seen before include "Small secluded valley" , "Manufacturer that relies heavily on Silicon" , "Deep hollow or small valley" , "Small wooded hollow or valley" , "Small valley; computer company" .)
(Other definitions for dene that I've seen before include "Sandy tract" , "Small valley" , "Deep wooded valley" , "North American Indian" , "Narrow wooded valley" .)