Premise: On the fourth side is an artificial lake stretching 8 km (5 miles) to the Rajasthan border, never sufficient, apparently, for the needs of the citadel, and so one of the probable reasons why Akbar did not settle here permanently.
Hypothesis: There is an artificial lake that stretches 8 kilometres to the Rajasthan border but it could not meet the needs of the citadel. 
Label: entailment