Abstract type "TravelTips" must resolve to an Object type at runtime for field "Query.travelTipBySlug". Either the "TravelTips" type should provide a "resolveType" function or each possible type should provide an "isTypeOf" function.
The full hike is quite difficult (6.3km and 853m of elevation) with the final part being the most difficult with some steep scree to climb. However, there is a point where you can stop above the hill, but before the scree. This point is about 2.4km in and 600m up and gives amazing views of Spray Lakes. But it is still steep.