What is the proof of gravity being curvature of spacetime?

According to general relativity gravity is an illusion caused by curvature of space-time, rather than real force. As I understand there is overwhelming experimental evidence to support general relativity.

Are there experiments that confirmed specifically gravity as curvature of space-time?

To clarify:

Was there an experiment that shown directly that observable space does not conform to Euclidean geometry? In example (but not limited to): observations of triangles whose angles don't add up to 180 degrees?

• @AccidentalFourierTransform Perhaps i'm misunderstanding "direct" here. Did we actually observe curvature of spacetime? I mean direct observation, ie. triangle with angles that didn't add up to 180 deg. I would assume that something like that would be an direct effect of curved space. – Koder Feb 11 '16 at 22:08
• For this question to make sense, you need to define what "curvature of space-time" is. – Ryan Unger Feb 11 '16 at 22:22
• @0celo7 "deviation of geometry of spacetime from Euclidean geometry" – Koder Feb 11 '16 at 22:34
• Geometry of spacetime? – Ryan Unger Feb 11 '16 at 22:37
• @0celo7 Am I using wrong term? I am no native speaker, perhaps this is an translation error? To elaborate, by "geometry of spacetime" I mean "Geometry of mathematical model that combines space and time". I was under the impression that GR was about defining gravity as gravity as a "geometric property of space and time" and this was correct term to use. – Koder Feb 11 '16 at 22:47

If I understand the intent of the question you are asking if we have ever directly measured the deviation of some geometrical object from flat spacetime. For example have we ever measured the internal angles of a triangle and come up with an answer different to $\pi$?