館内 and 構内: inside a building and within facility grounds
Compare an indoor rest area with a bus stop on university grounds, allowing the grounds to include places outside buildings.
Inside a library, hall, or similar building
館内, read かんない, means inside a building such as a library or hall. 館内に休憩室があります。 says that there is a rest area inside the building.
館内の案内は受付で聞けます。 says that information about the building interior can be requested at reception. This possibility differs from already having received the information.
Within a facility’s boundaries
構内, read こうない, means within the grounds of a school, station, factory, or similar facility. 大学の構内にバス停があります。 places a bus stop on the university grounds.
構内の地図で庭園の位置を確認しました。 says that someone checked the garden’s position on the grounds map. It does not state a visit to the garden.
Applying building and grounds boundaries separately
建物の外ですが、大学の構内です。 says that the location is outside the building but within the university grounds. Apply the boundary of 建物, read たてもの, separately from the grounds boundary.
館内の休憩室を探す means looking for a rest area inside the building, while 構内のバス停を探す means looking for a bus stop within the facility grounds. Both the target and search area differ.
Does 大学の構内にバス停があります。 establish that the bus stop is inside a university building?
Show the answer and why
No. It locates the stop within the university grounds. Whether it is indoors and its precise position need separate information.