The starting location is at N50° 42.939' E 7° 10.283

During this hunt, approximately 12 km long, you'll see a lot of ancient stuff.
Some of them tell old tales, other things are not as secret, but also somewhat significant for the rest of the world.

You can do the whole trip by bike, but there are some steep gradients. 
The last few meters to the cache can also be done only if you like to walk on difficult ground.
Driving by car may be another nice adventure.

Task No. 1:

When did the thunderbolt (Blitz) hit? ABCD
When did the excavations (Ausgrabung) begin? EFGH

Next location: N50° 4(A+C).(C)(G-B-C)(H) E 7° 1(G-H+A).(B+C+C)(F-G-C)(F-G+E)

Task No. 2:

Count the objects, obviously forming a geometrical shape. Note the number as IJ.

Next location: N50° 4(C).(J)(I)(J)  E 7° 1(A).(J-H+I)(A+B)(E)

Task No. 3:

Note the year this monument was built as KLMN.
Note the year when the famous died as OPQR.

Next location: N50° 4(K).(P+P+K+N)(M)(Q+R) E 7° 1(P).(Q+Q)(O+P)(R)

Task No. 4:

Another monument. Note the year it was built as STUV.
The area around will be worth some more inspections.

Next location: N50° 4(U-V).(T)(U)(Q) E 7° 1(U-T).(T-Q)(J)(U-S)

Task No. 5:

There's a height written on a stone. Note this as WXY.Z .

Next location: N50° 4(Z-X+P+W).(Z)(Y+P)(T-Y) E 7° 1(R).(Z-Y)(V)(V-W)

Task No. 6:

Now it's nearly done.
The full degrees are clear: N 50° und E 7°
Compute the latitude minutes as h - 13.3214
and the longitude minutes as r - 15.33255

Now find the location, where the cache is buried.

Use workers gloves to move some rocks.

The previous Cache was lost, so we decided to hide the new one at a more difficult location, sorry.
Reception will be very bad sometimes.
Better remember or print the spoiler photos.

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Hint: Near the end of a granite rubble field, hidden under some rocks.