When checking the caching map before we visited Belem, we thought there was a direct route through to this cache from Museu de Marinha but when we were there we couldn't find one. Instead, we came the long way round.
As we got close to GZ, I thought I'd spotted the hiding place and pointed it out to Mrs Stooby. She went for a closer inspection and confirmed that I had been correct. We quickly signed the log, then made our way to another cache we had on our list.
Thanks for the hide.