During the construction of a metro station, artefacts from various eras of history have been discovered. Now, the remnants of many historical eras are on display here. Check it out from the Dormturm of the Frankfurt Cathedral from where you get a different perspective of the whole complex.
The museum is open-air and accessible at all times.
Wikipedia (German) http://de.wikipedia.org/wiki/Arch%C3%A4ologischer_Garten_(Frankfurt_am_Main)
More information at Frankfurt's official website http://www.frankfurt.de/sixcms/detail.php?id=5021813&_ffmpar%5B_id_inhalt%5D=5021014
Phone +49 (0) 69/212-3 58 96
Address Karmelitergasse 1 Frankfurt, Germany
Coordinates 50°6'38.002" N 8°41'3.484" E