An inn. According to L&M, it was at the top of Gabriel’s Hill, although this text says there was a Bell in on Week Street, which adjoins the top of Gabriel’s Hill. So the map location is very approximate.
The overlays that highlight 17th century London features are approximate and derived from Wenceslaus Hollar’s maps:
Open location in Google Maps: 51.274105, 0.523095
Chart showing the number of references in each month of the diary’s entries.