Lincoln Castle and the Collection Museum have both reserved an hour a week for the elderly and most vulnerable.
Each Thursday, between 10am and 11am, shielding visitors will have priority access to a reduced number of tickets for the sites.
Paul Mason, visitor experience manager, explains: "We recognise the reassurance our safety measures offer is a huge factor in whether people decide to visit.
"We hope by having an having an hour where we significantly reduce the number of people allowed in the venues, plus an extra enhanced clean before entry – those who are shielding will have the confidence to visit us.
"We're delighted to have safely reopened Lincoln Castle, its Wall Walk, Victorian Prison and its Magna Carta Vault, and the Lincoln Museum and many people have visited. Both sites have achieved Visit England's 'Good to Go' accreditation which means they are Covid- 19 secure."
For more information, visit the Lincoln Museum website.