In the list of Irish counties by highest point, Longford ranks third lowest. Only Meath and Westmeath have lower maxima. In general, the northern third of the county is hilly, forming part of the drumlin belt and Esker Riada stretching across the northern midlands of Ireland. The southern parts of the county are low-lying, with extensive areas of raised bogland and the land being of better quality for grazing and tillage. The River Shannon marks the county's border with Roscommon while the Rivers Inny and Tang form much of the boundary with Westmeath.