Grain Tower Battery / Number 1, The Thames

A maritime fort constructed in the 1860s in the middle of the Thames Estuary is on the market for half a million pounds, or roughly $835,000.

With its fifteen-foot thick walls and insanely daunting approach—accessible on foot only at low tide and, even then, after a squelching walk across seemingly endless mudflats — it’s certainly a good option if you’re looking for solitude — via BLDGBLOG