The "Oldest, Highest, Longest, Smallest" page.

OLDEST:

CHURCHES:

The oldest church in Britain is probably St. Peter's-on-the-Wall at Bradwell-on-Sea, Essex which dates from the 7th Century.

The oldest log church in the world is St. Andrew's Church at Greensted, near Ongar, Essex although that only really applies now to the walls of the nave, which date from the 11th Century.

The oldest cathedral in Britain is Durham Cathedral, started in 1093, which is also the oldest Norman building.

The oldest church door in England (Saxon - 1060) is still on St. Botolph's church in the village of Hadstock in Essex.

The oldest working turret (or tower) clock in England is in the tower of St. Mary's Church in Rye, Sussex.
INNS:

The oldest inn in Britain is, officially, Ye Olde Fighting Cocks in St. Albans, Hertfordshire - it's listed in the Guiness Book of Records.
BRIDGES:

The oldest bridge in Britain is thought to be Tarr Steps on Exmoor, Somerset which is a Clapper Bridge.
STRUCTURES:

The oldest surviving Roman structure in Britain is the Balkerne Gate together with the Roman wall at Colchester, Essex.

The oldest timber-framed barn in the world is Barley Barn in Cressing Temple barns, Braintree, Essex.

CHURCHES:

The longest Medieval cathedral in the world is Winchester Cathedral, Winchester, Hampshire.
RIVERS:

The longest river in Britain is the River Severn which runs for 220 miles from it's source on the slopes of Plynlimon, in Ceredigion (Cardiganshire), Wales and finally discharges into the Bristol Channel.

The longest river in England is the River Thames at 215 miles long.
LAKES:

The longest lake in England is Lake Windermere in the Lake District at 10.5 miles.
FOOTPATHS:

The longest footpath in England is the South West Coast Path at 630 miles.

The longest footpath in Wales is the Pembrokeshire Coast Path at 186 miles.

The longest footpath in Scotland is the Southern Upland Way at 211 miles.
CAVES:

The longest Show Cave in Britain (open to the public) is White Scar Cave near Ingleton in the Yorkshire Dales with about 0.5 miles of passage.

The longest cave system in Britain is the Three Counties System in the Yorkshire Dales with 54 miles of passages. This system can be visited only by experienced cavers.

MOUNTAINS & HILLS:

The highest mountain in Britain and Scotland is Ben Nevis (4368 feet) near Fort William, Scotland. The highest mountain in Wales is Snowdon (3526 feet) and the highest in England is Scafell Pike (3210 feet), Cumberland (Cumbria) in the Lake District.

The highest man-made hill in Europe is Silbury Hill near Avebury, Wiltshire.
INNS:

The highest Inn in Britain is the Tan Hill Inn (1742 feet), north of Keld, Yorkshire and is located on the route of the Pennine Way long distance path.
RAILWAY STATIONS

The highest railway station (3494 feet) in Britain is on Snowdon (3560 feet) in Wales although that is a specialised rack and pinion mountain railway and is not part of the normal railway network. The highest, and probably the most remote, station on the normal railway network is on Rannoch Moor (1350 feet) in Scotland.

LAKES:

The deepest lake in Britain is Loch Morar in the Highlands of Scotland at 1017 feet deep.

The deepest lake in England is Wast Water in the Lake District at 250 feet deep.
CAVES:

The deepest cave in Britain is Ogof Ffynnon Ddu in Wales at 1,010 feet deep and the deepest single drop is Gaping Gill
at 350 feet.

RIVERS:

The shortest river in Britain is the River Morar which runs from the deepest freshwater loch/lake in Europe (Loch Morar) to the sea and is just short of 1000 yards long.

INNS:

The smallest Inn in Britain is The Nutshell, Bury St. Edmunds, Suffolk at 15ft x 7ft 6in. I understand that they don't provide food as there's no room to eat it.
CHURCHES:

The smallest church in Britain is Bremilham Church, on a farm at Foxley-cum-Bremilham near Malmesbury, Wiltshire, and measures just 11 feet by 10 feet. The smallest church still holding regular services is Culbone Church near Porlock Weir, Somerset.
CITIES:

The smallest City in Britain is St. David's, Pembrokeshire, Wales. Although it is only the size of a village it does have a cathedral.

The smallest City in England is Wells, Somerset.

LAKES:

The largest Lake in England is Lake Windermere in the English Lake District and the largest lake in Great Britain is Loch Lomond in Scotland.
STONE CIRCLES:

The largest Stone Circle in the world is Avebury in Wiltshire covering 28 acres and being nearly a mile in circumference.
CAVES:

The largest cave opening in Britain is Hull Pot in the Yorkshire Dales at 300 feet long, 60 feet wide and 60 feet deep. The largest cave mouth in Wales, and one of the largest in Great Britain, is Porth-Yr-Ogof near the village of Ystradfellte.

The Norman Wheel Window in Castle Hedingham Church is one of only five in the whole country.
This round church in Cambridge is one of only four in England discounting the ruined one in Ludlow Castle.