"Return to Ravenholm," aka "Half-Life 2: Episode 4," was a Half-Life 2 episode set in the spooky abandoned town. It's been canceled for a few years now, but we've gotten a better look at the game that could have been thanks to some new concept art and animation tests. It was in development at Dishonored developer Arkane Studios around 2006, but was ultimately scrapped.
Valvetime revealed the new shots, with Rock Paper Shotgun's Craig Pearson confirming their authenticity. According to Valve's Marc Laidlaw, the project had been canceled because the defining qualities of Ravenholm (headcrabs and zombies) were feeling "played out," and the game's placement in the timeline of the other episodes was a "creative constraint." But if you're curious to see the small bits remaining of the project, check out the video below.