Sparta, like all Greek states, had rigid racial laws of citizenship against half-bred and foreigners, and for many generations, it saw its citizenry (that is its army) decline. Sparta adopted customs of publicly humiliating unmarried and childless male citizens, in the theater, they had to give up their sites to youngsters, and in some festivities, they were forced to dance naked in a circle singing self-debasing songs. They celebrated annual ceremonies where marriageable girls were paraded naked, trying to inflame desire and attract suitors. Boys, from age 7, were educated in the army, where homosexuality was de rigeur, so they were inexperienced and terrified of women. To help them actually to be able to consummate the union, it took place in private in obscurity, and the bride - with a shaved head - was dressed up in men's clothes. Childless married women were legally impregnated by an army comrade or a friend, free of the stigma of bastardy.
Nothing helped, Sparta's citizen body steadily declined to the point that there were not enough able Spartiates to govern its foreign possessions. To refill the infantry, Sparta called for Helot (slave) recruits, and thousands volunteered. When formed into battalions, the Spartans were frightened by the high military quality of the new corps, and secretly killed them all. In the end, the Spartan army numbered less than a thousand and there was no one to oppose the Boeotian invasion.
Later, in Roman times, Sparta became a tourist attraction, with actors replaying Spartan religious rituals and war dances. Athens left a large literary and political legacy, Sparta left nothing.