A vanishing, sulphurous stain

A sulfurous "stain" in the lower level disappears when it is touched. Employees have reportedly seen orbs near the stain.

Ties between Baltimore and the Ouji board

Not commonly known, the Ouiji board has strong ties to Baltimore. The design known today was patented here in Baltimore by Elijah Bond, although William Fuld is credited with it's design. These boards sold even today in toy and game stores are potentially much more than a mere entertainment; many have found that entities contacted via the board sometimes decide to hang around and some of these are not of the nice variety.

Once almost a Prime Meridian and discovery place of satellites of Mars

The Old Naval Observatory once almost became a Prime Meridian of the United States, to be used as a foundational basis point for surveyed measurements. Home of master optician Alvan Clark's first large, 26-inch refratory telescope, it was also, in 1877, the discovery point, by Asaph Hall, of Mars' satellites.