So here is the best account I have seen of the (latest) tomb of Romulus
Roma, straordinaria scoperta al Foro: torna alla luce un ipogeo con sarcofago legato a culto di Rom… roma.repubblica.it/cronaca/2020/0… via @repubblica
Roma, straordinaria scoperta al Foro: torna alla luce un ipogeo con sarcofago legato a culto di Rom… roma.repubblica.it/cronaca/2020/0… via @repubblica
Location is said to be under the stairs which Alfonso Bartoli constructed in front of the surviving Curia Julia, and here are some before and afters. Bartoli described his work in his book Curia Senatus: Lo scavo e il restauro 
there is a sarcophagus in tufa, in an underground chamber, and a round stone nearby which is suggested to be an altar. Not clear so far how this is being dated to the 6th c BCE.
Boni had already published this in NSc. 1900 p299-300, and said it contained pebbles, fragments of pottery, shells and a piece of red plaster.
Why Romulus? ancient commentators on a poem of Horace (Epode 16) quote Varro to say that Romulus was buried near the Rostra, in a place marked out by sculptures of lions.. (Spoiler, this might not be an entirely true story...)
1. Varro's text is pro rostris (in front of the Rostra) acc. to Ps.Acron and post rostra (behind it), acc. to Porphyry, which used to be taken as the worse reading, but is the one being used now.
Burials in the Forum, and indeed generally within the city after the 7th c BCE are extremely rare, so this is a special find. Another proposed location for Romulus' tomb is underneath the nearby Lapis Niger, a black stone which marked an early complex of monuments.
One of Varro's few rivals in topographic and antiquarian knowledge, Verrius Flaccus, probably thought Romulus was buried here, although we also have references to a tomb of Faustulus (the shepherd who adopted Romulus and Remus) and Hostus Hostilius (allegedly a contemporary).
It will be very interesting to hear more from @alfonsrusso and @SoprArcheologia about the dating. Meanwhile it looks as if there were a few 'special' tombs which were allowed into the forum, some of which were at some point associated with the stories of the kings.
It is at least intriguing that the senate house which was begun by Julius Caesar and completed by Augustus, both of whom claimed descent from Romulus, was so close to this burial (not least because Romulus was said in one story to have been killed by the senators).
Saying anything more will require quite a bit more work, information and nuance, but it all shows how exciting the study of early Rome is right now, as we also know from @NTerrenato 's super work.
