If in doubt, RTFM
The German AIP ENR 1.6 is the origin of this particular comment on the Jepp maps. I've reproduced it here in full with the relevant bits emboldened. Basically, you should be at or about 2000 feet, but airspace constraints are one of a number of reasons that may reasonably force you lower.
The text in full:
"(1) Aircraft shall not be flown below the minimum safe height except when necessary for take-off and landing. Minimum safe height is the height at which neither an unnecessary noise disturbance in the sense of § 1 para (2) nor unnecessary hazard to persons and property in the event of an emergency landing are to be feared; however, over cities, other densely populated areas, and assemblies of persons this height shall be at least 300 m (1000 ft) above the highest obstacle within a radius of 600 m, and elsewhere at least 150 m (500 ft) above ground or water. Gliders, hang-gliders and paragliders may be operated below a height of 150 m if necessary for the kind of operation and if danger to persons and property is not to be feared.
(2) Aircraft shall not be flown below bridges and similar constructions nor below overhead lines and antennas.
(3) Cross-country flights according to VFR with power-driven aircraft shall be conducted at least 600 m (2000 ft) above ground or water, unless
, for safety reasons according to para (1) sentence 2, a higher level has to be maintained. Cross-country flights below 600 m (2000 ft) above ground or water taking into consideration the regulations under para (1) and (2) may be commenced and conducted, if the adherence to other rules and regulations according to the „Luftverkehrs-Ordnung“, in particular the adherence to the airspace structure according to § 10, the VFR rules according to § 28 or the ATC clearances, require a lower level.
(4) For flights conducted for special purposes, the local competent Aeronautical Authority of the Land may grant exceptions.
(5) For flights in accordance with Instrument Flight Rules, § 36 applies.
(6) Para (3) does not apply to military low level flights and flights including missions of the Federal Border Police, the civil defence and disaster control, and the police forces of the Lands. "