The government owns assets worth £337 billion, the Treasury has calculated.
The Ministry of Defence owns £93bn of assets
The Ministry of Defence tops a list of 19 departments on the National Asset Register, owning assets worth £93bn.
The Department for Transport comes second with assets of £81bn, followed by the Department of Health with £40bn worth of assets as of March 2005.
The register records all assets with a value above £1m owned by central government departments, except the security and intelligence services.
The defence figure includes overseas bases, such as those in Cyprus, the Falklands Islands and Germany.
Downing St value
Domestic assets include Edinburgh Castle, worth £1.96m, and barracks, museums and ranges throughout the country.
Defence transport assets total £38bn, including 25 Hercules C130J transport aircraft worth £753m.
Numbers 10 and 11 Downing Street, owned by the Cabinet Office, are valued at £15 million.
It also owns "antiques and works of art" valued at £7.7m and furniture and fittings of £1.9m, the register showed.
Within the Department of Health, the NHS trusts and foundation trusts owned the largest chunk, with assets of £32bn, while the primary care trusts owned assets of £5.7bn.
Chief secretary to the Treasury, Stephen Timms, said: "The 2007 NAR will encourage departments to make the best possible use of their existing asset base by exploiting under-utilised assets and disposing of assets no longer required for service delivery.
"This improvement in asset management practices will enhance the efficiency and effectiveness of the UK public sector."