1) Bramble Woods South Outpost "Lookout Tower" -this is a no brainer. There is a "lookout tower" on the hilltop at the Bramble Wood Ranger Outpost. A telescope that lets you look into the North-Wood, as well as towards the "bugbear Camp" to the west, and also to the TRADE ROAD (the area where the Bridge/gate that is always gettin bashed is located.
2) Myon's Upper Mythal Portal - Telescope should let you look across to similar locations as the Dreaming Tree (maybe it should just be duplicated and added there?)
3) Heartwood Treehouse - nuff said.
4) Brog Gates, at the top of 10,000 Stair. -this should give you the chance to look down on the falls area, maybe some other similar regions too... i mean.. c'mon... it's atop a giant arse mountain!!!
5) The Weatherstone - There currently is a placable telescope there, but it is non-functioning. This location is also cliff-based and it's overlook should grant very impressive views! I mean.. c'mon.. you hiked all the way up there..r, right???
--those are my top 5 locations I'd put telescopes that let you peer into distant or adjacent territories... and the list is my suggested order of priority.
