If you go to the lost sector in the upper left corner of Trostland, go through to the open area at the end when you fight the fallen go along the left side of the area. It's an EXACT copy of Memento from D1! The busted up ramp leading from the old zone C, the hallway with the file cabinets, even the sniper ramp on the outside of the building is there! The outside architecture is the same, and the ABS Kastner sign is even there.
It's definitely not a pvp map, but I think it's extremely cool that Bungie threw this in there as a little easter egg. If anyone has seen another area like this I'd love to hear about it. I posted a video on Youtube showing the area. What do you think? Btw I have side by side comparison pics available.